RU2778193C2 - Method for cryogenic air separation and air separation installation - Google Patents

Abstract

FIELD: separation.

SUBSTANCE: method for cryogenic air separation using air separation installation (100-900) is proposed. In mass transfer column (13), the first liquid fluid and the second gaseous fluid are subjected to mass transfer with each other. The third gaseous fluid is removed from column (13). The fourth liquid fluid is supplied from column (13) to low-pressure column (12), and the fifth fluid is formed, using at least part of oxygen-enriched liquid removed from column (12). The second fluid is formed, using oxygen-enriched liquid removed from high-pressure column (11). Oxygen-enriched liquid from column (11) and cubic liquid from column (13) are mixed and partially evaporated, using a capacitor-evaporator, in which a liquid flow, which contains at least part of oxygen-enriched liquid from column (11), and at least part of cubic liquid from column (13), is passed under pressure through an evaporation zone, using its own pressure, and partially evaporated in it. The fifth liquid fluid is removed from column (13) between a point of supply of the first fluid and a point of supply of oxygen-enriched liquid, and supplied to column (12) downstream the fourth fluid supplied to column (12).

EFFECT: reduction in energy consumption.

13 cl, 11 dwg

Description

The invention relates to a method and plant for cryogenic air separation according to the respective preambles of the independent claims.

State of the art

(Ed.), Industrial Gases Processing, Wiley-VCH, 2006, в частности в разделе 2.2.5, «Cryogenic Rectification».The production of air products in the liquid or gaseous state by cryogenic air separation in air separation plants is known and described, for example, in H.-W.

(Ed.), Industrial Gases Processing, Wiley-VCH, 2006, in particular section 2.2.5, "Cryogenic Rectification".

Pure oxygen is required, at least not exclusively, for a variety of industrial applications. This creates the possibility of optimizing air separation plants in terms of their installation and operation costs, in particular their energy consumption. For details refer to the technical literature, e.g. F.G. Kerry, Industrial Gas Handbook: Gas Separation and Purification, CRC Press, 2006, section 3.8, "Development of Low Oxygen-Purity Processes". For example, to produce pressurized oxygen gas of relatively low purity, air separation units having so-called mixing columns can be used. In this regard, references are made to EP 3179186 A1 and the literature cited there.

In the method proposed in US 5704228 A for evaporating a liquid by heat exchange with a condensed gas, the pressure of the evaporating liquid is reduced and said liquid is enriched with a less volatile component. According to an alternative approach, it is possible to enrich the gas with less volatile constituents. You can use a mixing column. Mixing column methods are also described in JP 2000-258054 A, US 2001/0003909 A1, CN 106123489 A and EP 0982554 A1.

Typically, an oxygen-rich liquid is fed into the mixing column near the top and pressurized gaseous air, the so-called mixing column air, near the bottom, said liquid and air being subjected to mass transfer. In this way, the so-called "impurified" oxygen can be recovered from the top of the mixing column and removed from the air separation plant as a product gas. The liquid that is separated at the bottom of the mixing column can be fed to a location that is suitable in terms of energy and/or separation technology in the distillation column system used. By using a mixing tower, in particular, it is possible to reduce the energy required to pressurize the oxygen product at the expense of the purity of the oxygen product.

In air separation plants containing mixing columns, the maximum usable so-called injection equivalent is significantly limited for reasons explained in more detail below. Therefore, it is also true that the energy savings possible with an increase in the injection equivalent in air separation plants is limited.

Therefore, the purpose of the present invention is to eliminate this obstacle, thus increasing the efficiency of air separation in the respective installations and, as far as possible, reducing unnecessary costs.

Description of the invention

This goal is achieved by using the method and installation of cryogenic air separation, having the corresponding features of the independent claims. Advantageous configurations are the subject of the respective dependent claims and the following description.

First, the following is a more detailed explanation of some of the terms used in the description of the present invention and its advantages, as well as the prior art serving as a basis.

Air separation processes for generating cold and liquefying material streams at various locations may use turboexpanders, also referred to as "turbines" for short, as is well known to those skilled in the art. Reference is made below to "Claude turbines", "Lachmann turbines" and "pressurized nitrogen turbines". As regards the function and purpose of such turboexpanders, references are made to the technical literature, e.g. F.G. Kerry, Industrial Gas Handbook: Gas Separation and Purification, CRC Press, 2006, in particular sections 2.4 "Contemporary Liquefaction Cycles", 2.6 No. "Theoretical Analysis of the Claude Cycle" and 3.8.1 "The Lachmann Principle".

In the case of a two-column system, the cooled pressurized air is expanded from the relatively high pressure level to the pressure level of the high-pressure column by means of a Claude turbine and fed into the latter. On the contrary, with the aid of a Lachmann turbine, cooled pressurized air is expanded to the pressure level of the low pressure column and fed into the latter. Finally, the pressurized nitrogen turbine expands the nitrogen from the high pressure column.

In a conventional Lachmann turbine ("injection turbine"), pressurized air is expanded, which is cooled (and in this example not further compressed), from a pressure level of, for example, about 500 kPa to 700 kPa (abs.) (5.0 to 7.0 bar (abs.)), the normal pressure level at which the high pressure column operates, or from another pressure level, to a pressure level, for example, from about 120 kPa to 160 kPa (abs.) (from 1.2 to 1.6 bar (abs.)), the typical pressure level at which the low pressure column operates. The air expanded in the Lachmann turbine is fed ("injected") into the low pressure column. The expansion of the respective feed fraction is possible due to the indicated pressure difference between the high pressure column and the low pressure column.

However, the air thus expanded into the low pressure column interferes with fractionation and for this reason the amount of air capable of being expanded into the injection turbine and thus capable of generating cold in this way for the respective plant is substantially limited, in other words, limited even without the use of a mixing column. Nitrogen-rich air products that are removed from the high pressure column and discharged from the air separation unit also affect the fractionation accordingly. The amount of air fed into the low pressure column plus nitrogen removed from the high pressure column and discharged from the air separation unit can be determined in relation to the total air fed into the distillation column system. The value obtained here is nominally referred to as the "injection equivalent".

Thus, the injection equivalent is defined as the amount of pressurized air that is expanded into the low pressure column of the separation plant by the injection turbine, plus the amount of nitrogen that is possibly removed from the high pressure column and neither recycled as a liquid reflux to the high column itself. pressure, nor injected as a liquid reflux into the low pressure column, with respect to all the pressurized air supplied to the distillation column system. Here, the nitrogen that is removed from the pressure column may be pure or substantially pure nitrogen from the top of the pressure column, however, it may also be a nitrogen-rich gas that can be recovered, with a lower nitrogen content, from the pressure column from the area below the top.

If an injection turbine is used in the respective air separation plant and the pressurized air amount M1 is expanded in the latter, the nitrogen amount M2 is removed from the high pressure column and removed from the air separation plant as a liquid and/or gaseous nitrogen product, in other words not used as a return flow into the high and/or low pressure column, and the amount M3 of pressurized air is supplied in general to the distillation column system, the injection equivalent E in the respective plant is calculated as

In general, increasing the injection equivalent in an air separation plant results in a reduction in energy requirements.

The expansion of the nitrogen or nitrogen-rich fluid from the high-pressure column in the pressurized nitrogen turbine can be carried out before said nitrogen is fully heated in the main heat exchanger (in the so-called cold pressurized nitrogen turbine) or after that (in the so-called warm nitrogen turbine under pressure). pressure). Then the expanded nitrogen can be used, in particular, for the regeneration of adsorbers. The use of a pressurized nitrogen turbine also reduces the energy consumption of the air separation plant. However, pure or impure nitrogen from the high pressure column expanded into the pressurized nitrogen turbine also contributes to the injection equivalent, since said nitrogen is not used as a reflux in the high and/or low pressure column.

If the pressurized nitrogen turbine is supplied with nitrogen from the top of the high pressure column, said nitrogen is correspondingly pure. However, it is also possible to supply nitrogen with impurities from the high pressure column to the pressurized nitrogen turbine. In the latter case, the corresponding pressurized nitrogen turbine is also referred to as a "pressurized nitrogen turbine with impurities". The pressurized nitrogen turbine is characterized in that a nitrogen-rich fluid is fed into it from a high pressure column in which the nitrogen content of the fluid is lower than the nitrogen content of the high pressure column overhead, in other words below the maximum nitrogen content of the high pressure column.

The reason for the lower injection equivalent available in conventional mixing column processes relative to other cryogenic air separation methods is in particular that the air stream fed to the mixing column is not optimally included in the double column fractionation process. In this regard, in particular, the oxygen available in this air stream completely passes through the high and low pressure column. Said oxygen is discharged in the form of a mixing column overhead from the air separation unit. Conversely, the nitrogen contained in the air stream to the mixing column remains (following the mixing column transfer process) almost entirely in the bottom liquid of the mixing column. Said bottom liquid typically has an oxygen content of approximately 65% and, in known methods, is fed into the low pressure column at a feed point corresponding to this oxygen content.

However, from a separation technology point of view, said feed point is in a region of the low pressure column that is relatively deep, in other words, at a point where the oxygen content is still relatively high. The distillation or separation section located below the feed point can already be considered an oxygen section, since no additional feed to the low pressure column is carried out below the feed point for the bottom product of the mixing column. Therefore, it is necessary to separate the nitrogen from the air stream into the mixing column (which passes into the low pressure column in the form of the bottom liquid of the mixing column) from a very deep position in terms of separation technology. However, under these conditions, said separation is extremely complex and requires a relatively high power on the main capacitor. Therefore, it is necessary to reduce the injection amount into the low pressure column, or said injection equivalent, accordingly, in order to be able to perform the separation satisfactorily.

The devices used in the air separation plant are described in the cited technical literature, for example in Haring in section 2.2.5.6 "Apparatus". Where the following definitions therein do not deviate from this, therefore, explicit reference is made to the cited technical literature regarding linguistic usage in the context of this application.

The distillation or separation columns that are used in cryogenic air separation contain so-called separation sections. The separation section is an area of the distillation column that is equipped with internal separation devices or separation structures such as sieve trays or structured or unstructured seals. The separation section is characterized in particular in that it is located between two points of supply of fluids to the respective distillation column or is located between a point of supply and a point of removal of the fluid, and that between these two points of supply or a point of supply and a point of removal there are no no additional points of supply or points of removal of the fluid in the distillation column or from the distillation column. The respective feed points are pipelines for supplying fluids to the distillation column, said pipelines being used for regular supply during the operation of the respective air separation unit. The same applies accordingly for deletion points. However, a corresponding distillation column also containing additional holes between the feed points cannot be ruled out. These additional openings, however, are not used during normal operation of the air separation unit. The terms "distillation" and "rectification" are used herein synonymously.

Within this usage, liquids and gases can be rich or lean in one or more components, where "rich" can represent a content of at least 50%, 75%, 90%, 95%, 99%, 99.5%, 99.9% or 99.99% and "poor" may represent a content of no more than 50%, 25%, 10%, 5%, 1%, 0.1% or 0.01% on a molar, mass or volume basis. The expression "predominantly" may correspond to the definition of "rich". In addition, liquids and gases can be enriched or depleted in one or more components, where these expressions refer to the content in the initial liquid or initial gas from which the liquid or gas was obtained. A liquid or gas is "enriched" if said liquid or gas has an appropriate component content of at least 1.1 times, 1.5 times, 2 times, 5 times, 10 times, 100 times, or 1000 times the content of the initial liquid or initial gas, and are "lean" if the specified liquid or gas has a content of the corresponding component that is not more than 0.9 times, 0.5 times, 0.1 times , 0.01-fold or 0.001-fold content of the content in the initial liquid or in the initial gas. Here, when "oxygen" or "nitrogen" is mentioned, for example, this is also to be understood as a liquid or gas that is rich in oxygen or nitrogen, but does not have to consist solely of them.

To characterize pressures and temperatures, this application uses the terms "pressure level" and "temperature level", which are intended to express that the pressures and temperatures in the corresponding installation do not need to be used in the form of exact pressure and temperature values to implement the idea of the invention. However, such pressures and temperatures usually vary within specific ranges, such as ±1%, 5%. 10%, 20% or even 50% of the average. Here, the respective pressure levels and temperature levels may lie in separate intervals or in overlapping intervals. In particular, pressure levels, for example, include inevitable or expected pressure losses. The same applies accordingly to the temperature levels. The pressure levels given here in bar are absolute pressures.

Advantages of the Invention As explained, the injection equivalent used in known mixing tower processes is significantly lower compared to other cryogenic air separation methods. Therefore, the area of use of the respective methods is significantly limited or, in some cases, additional funds are required, which lead to a noticeable increase in costs. In this regard, it is necessary to have a multi-layer compressor for gaseous nitrogen if, in addition to the oxygen product, a relatively large amount of pressurized nitrogen is also supplied.

It is also the case that in the case of increased liquid production (which is significantly greater than the flush amount required to discharge undesired components), mixing column methods are relatively disadvantageous, since in this case either a relatively poor oxygen output must be tolerated (resulting in high operating costs due to the high injection quantity) or other measures are required, such as an additional medium pressure turbine in combination with so-called high-pressure air integration. The reduction in oxygen output comes from the fact that in case of increased liquid production, a higher cold power is required, however, this can only be met with a higher number of turbines or a higher injection amount. However, in conventional mixing towers this quickly leads to a decrease in the oxygen yield, in other words more air molecules (more feed air) are required in the process to produce the same number of oxygen product molecules. The use of additional mentioned means leads to increased costs for mounting equipment for the respective installations.

If one considers a heat exchanger in an optimized (but conventional) mixing tower process, then, even in the case of pure gas production, said heat exchanger needs to be relatively large in size, since the turbine power (or the amount of injection into the turbine) is also very dependent on the so-called losses to transfer to the warm end of the heat exchanger. Therefore, in the mixing column process, the transfer loss must be kept relatively low by increasing the transfer surface area in the heat exchanger.

The present invention overcomes these disadvantages in such a way that not a stream of air, but instead of it, a stream of another substance is fed into a mixing column or into a comparable device used for mass transfer (such a device is also simply referred to below as "mixing column"). In this case, within the scope of the present invention, the oxygen-enriched liquid from the high pressure column, in particular its bottom liquid, is used. Said liquid, which is already enriched in oxygen with respect to atmospheric air, is in particular fed in liquid form into a mixing column or a suitable device and is mixed during the process with the liquid flowing down in a mixing column or a suitable device, in particular at the bottom. By means of an evaporator, the mixed liquid is evaporated as explained below, and the resulting vapor rises in a mixing column or a suitable device. Thus, according to the invention, the gas phase in the corresponding mixing column or in the corresponding device is not formed with the aid of pressurized air, but rather in this alternative manner.

The evaporation process in this case is carried out, in particular, by (partial) condensation of the air stream at an appropriate pressure. In particular, the air thus liquefied can then be subcooled and fed into the low pressure column at a suitable feed point. However, said feed point is located relatively high in the low pressure column, in other words at a position where the oxygen content is already relatively low. The liquid withdrawn from the bottom of the high pressure column is thus as if it were (from the point of view of the liquid balance) divided into two fractions, namely the first fraction, which is enriched to some extent with oxygen by partial evaporation in the condenser of the mixing column, and liquid air. This separation provides a better optimization of the liquid/vapor (L/V) ratios in the low pressure column and thus a better approximation of the equilibrium and operating lines on the MacCabe-Thiele diagram. Therefore, within the scope of the present invention, an additional separation section is advantageously provided in the low pressure column. A portion of the bottom liquid from the high pressure column (possibly also mixed with liquid flowing down in the mixing column) is evaporated by liquefying air and passed in gaseous form to the mixing column.

Here, the evaporated amount approximately corresponds to the air liquefied in the process (which is then fed into the low pressure column). Therefore, a corresponding analogy arises: the bottom liquid from the high-pressure column is practically divided between two liquid fractions of different composition.

However, a significant advantage of the compound according to the invention is that the feed air is carried entirely into the distillation column system and can be suitably used there to produce air products. As mentioned, in conventional processes, the air stream fed into the mixing column is not optimally included in the double column fractionation process and, in particular, the oxygen present in this air stream is completely passed through the high and low pressure column. However, said air flow does this within the scope of the present invention. Thus, rectification ratios are markedly improved, and costs required for rectification are reduced. In this regard, no oxygen molecules pass through the distillation columns, as in conventional methods (all oxygen is treated in said columns according to separation technology), and no excess nitrogen accumulates in the low pressure column, which must be separated at great expense. In this way, the power of the main condenser can be markedly reduced or, in a suitable installation, the injection equivalent and the associated possible energy savings can be significantly increased.

Through the use of the present invention, significantly higher efficiency is achieved compared to conventional mixing column methods. The use of the present invention also makes it possible in some cases to significantly reduce the volume of the main heat exchanger. This is possible, in particular, due to the significantly greater injection that the present invention allows. In addition, within the scope of the present invention, if air is supplied to the low pressure column in this way, only one generator turbine can be used. There is no need for two blocks, which are required in conventional mixing tower processes for the corresponding semi-load or liquid cases. In addition, the result is markedly smaller dimensions of various parts such as the pressure column and the main condenser.

In order to achieve the above advantages, the present invention is based on a cryogenic air separation process using an air separation plant comprising a distillation column system, which comprises a high pressure column operating at a first pressure level, a low pressure column operating at a second pressure level, below the first pressure level, and a mass transfer column operating at a third pressure level. The mass transfer column can be operated in particular at a pressure level which lies between the pressure level of the high pressure column and the pressure level of the low pressure column. The mass transfer column can generally be designed to be comparable to a known mixing column. In particular, it contains, for the fluids explained below, points of entry and exit, in each case at suitable heights, and contains mass transfer structures, which can be designed, for example, in the form of sieve trays or in the form of structured or unstructured packings. As explained below, within the scope of the present invention, the mass transfer column corresponds to a condenser-evaporator which operates as explained below. In addition, within the scope of the present invention, the mass transfer column, as explained below, is equipped with an additional intermediate liquid removal point and may in particular comprise an additional separation section associated therewith. Within the scope of the present invention, means are accordingly provided for supplying the removed liquid to the low pressure column.

In the mass transfer column, a liquid first fluid with a first oxygen content and a gaseous second fluid with a second oxygen content below the first oxygen content are subjected to mass exchange with each other, where the gaseous third fluid with a third oxygen content reduced relative to the first oxygen content, is removed from the mass transfer column and at least partially discharged from the air separation unit, and a liquid fourth fluid with a fourth oxygen content corresponding to at least the second oxygen content is removed from the mass transfer column and at least partially fed into the low pressure column. In this regard, the operation of the mixing column used in the context of the present invention therefore corresponds to conventional mixing columns in which the respective material streams (in this case, the liquid stream from the low pressure column and the air stream under pressure) are subjected to mass transfer, and the top gas and bottom gas the liquid is removed from the mixing column.

Similarly, as in the usual case, during the operation of the mixing columns in the framework of the present invention, the first fluid is formed here using oxygen-rich liquid from the low pressure column. In particular, said liquid without further modification is introduced in liquid form into the mass transfer column in the upper region, and it percolates downward in said column.

However, according to the invention, it is envisaged that the second fluid is formed using an oxygen-enriched liquid removed from the high pressure column, in particular the bottom liquid of the high pressure column. In this case, "second fluid" refers here to the fluid rising in gaseous form in the mass transfer column. Within the scope of the present invention, this is achieved by additional use of the liquid formed in the mass transfer column, in particular its bottom liquid. The oxygen-enriched liquid removed from the high pressure column is vaporized to form a second fluid. Here, within the scope of the present invention, said liquid is evaporated together with the liquid formed in the mass transfer column. Evaporation is carried out using an evaporator condenser, which is described in more detail below, in particular in indirect heat exchange with compressed and cooled feed air.

Within the scope of the present invention, the first oxygen content may be from 90 to about 99 mol. %, in particular from 93 to 98.5 mol. %, the second oxygen content can be from 30 to 45 mol. %, in particular from 33 to 40 mol. %, the third oxygen content can be from 80 to 98 mol. %, in particular from 90 to 97.5 mol. % and the fourth oxygen content can be from 55 to 72 mol. %, in particular from 59 to 67 mol. %. In the remaining fraction, said fluids predominantly contain nitrogen and, to a lesser extent, noble gases.

These measures make it possible to achieve the benefits mentioned. That here no pressurized air is fed into the mass transfer column, but rather steam is generated which rises in the mass transfer column, in particular by evaporating the oxygen-enriched liquid from the high pressure column and the liquid formed in the mass transfer column, in particular its bottom liquid , means that, as mentioned, the supply air is completely directed to the system of distillation columns and separated accordingly. In this way, as already explained, the fractionation ratios are markedly improved and the costs required for fractionation are reduced, in particular since no oxygen molecules pass through the distillation columns, and no excess nitrogen, which must be separated at great expense, accumulates in the low-temperature column. pressure. Please refer to the above additional explanations. In particular, the use of the present invention results in a reduction in separation costs and the required capacitor power. Thus, more air can be injected into the low pressure column, with the result that the overall energy consumption is reduced.

As mentioned, in the context of the present invention, the second fluid is the gas rising in the mass transfer column. As discussed in detail above, within the scope of the present invention, said second fluid is formed such that the oxygen-enriched liquid removed from the pressure column and the bottom liquid of the mass transfer column are vaporized by means of a flash condenser.

Within the scope of the present invention, the oxygen-enriched liquid from the pressure column that is used during the formation of the second fluid may have an oxygen content of 38 to 42 mol. %, for example, about 40 mol. %. As mentioned, the use of a suitable evaporator condenser makes it possible to condense or partially condense air in parallel with the corresponding evaporation, said air then being able to be fed in particular to the low pressure column.

It is particularly advantageous if the previously compressed and cooled amount of air is further cooled and at least partially liquefied in an evaporator condenser, said amount of air then being fed into the distillation column system. Here, the specified amount of air is referred to as the "first" amount of air for simplified reference or linguistic reference only. Here, the first amount of air can be compressed to a first pressure level, in other words to the pressure level of the high pressure column, but also to a higher or lower pressure level, to additional cooling and at least partial liquefaction. As explained below, the pressure level used here is matched, in particular, with the required pressure level of the gaseous third fluid that is removed from the mass transfer column and supplied as a gaseous oxygen product. For compression here, in particular, the main air compressor of the air separation plant is used, or said main air compressor is switched on together with other compressors or auxiliary compressors during compression. The cooling carried out initially before the post-cooling in the condenser-evaporator takes place in particular in the main heat exchanger. As explained, in this case, it is possible to completely liquefy the corresponding first amount of air and supply it to the low pressure column, or partially supply it to the high pressure column and the low pressure column. However, in some cases it can also be advantageous if the corresponding first amount of air is partially liquefied and fed, in particular in the form of a two-phase stream, into the pressure column.

In other words, it can be ensured that the compressed and cooled first amount of air is measured and compressed and cooled, so that said amount of air is at least partially liquefied in the evaporator condenser due to the additional cooling that is carried out here, where after liquefaction the first amount of air at least partially fed into the low pressure column or, for example, also into the high pressure column and into the low pressure column. As also explained below with reference to FIG. 3, it is also possible in this case to supply the first amount of air, at least partially liquefied in the evaporator condenser, only to the low pressure column. The specified amount of air, in particular, spend before this through the subcooler. In particular, in this case, it can be ensured that, in addition to the first amount of air, additionally compressed and cooled, although not liquefied, air is fed into the high-pressure column, which, in particular, is not carried through the evaporator condenser. The first amount of air, as well as non-liquefied air, supplied to the high pressure column is formed, in particular, using a compressed air stream that is removed on the cold side from the main heat exchanger of the respective plant. Said air stream is compressed, in particular, to the pressure level at which the high-pressure column operates.

In another configuration of the present invention, it can be ensured that the compressed and cooled first amount of air, which in this case is only partially liquefied in the evaporator condenser due to the additional cooling that is carried out here, constitutes the entire air supplied to the high pressure column, in other words, to the column high pressure do not supply any additional air, in addition to the first partial amount. In particular, in this case, in addition to the first amount of air and the second amount of air explained below, no additional air is supplied to the distillation column system.

In both cases, a medium is provided in the form of an appropriate amount of air, with which the oxygen-enriched liquid from the high pressure column can be evaporated together with the bottom liquid of the mass transfer column. The air used here can be fully fed into the distillation column system. In contrast to conventional mixing column methods, all feed air is therefore included in the fractionation.

As mentioned, the pressure level at which the feed air is passed through the evaporator condenser corresponds in particular to the required pressure level of the gaseous third fluid that is removed from the mass transfer column and provided as a gaseous oxygen product. In one configuration of the present invention, the first amount of air is compressed here to a first pressure level before at least partial liquefaction in the evaporator condenser. The gaseous third fluid is removed from the air separation unit or from the cooling chamber of such an air separation unit, in particular in this case at a relatively low pressure level. This last-mentioned pressure level may be, for example, approximately 320 kPa (3.2 bar) or less. Here, the average temperature difference in the main condenser, which connects the high pressure column and the low pressure column by heat exchange, may in particular be approximately 1K. In principle, a higher pressure of the oxygen product can be used, but this would lead to a first pressure level, which must be further increased for this. However, this is generally associated with poorer overall efficiency. For adequate compression, it is possible in particular to provide a main air compressor from which a first amount of air is removed at a first pressure level. It is also possible to ensure that the first amount of air is removed from the main air compressor at a lower pressure level, and said amount of air is then brought to the first pressure level using one or more auxiliary compressors or subsequent compressors. However, the first amount of air can also be suitably compressed in general only to a pressure level which is lower than the first pressure level, in particular, with subsequent feeding into a low pressure column. In such a case, it is possible to remove the gaseous third fluid from the mass transfer column of the air separation plant or from the cooling chamber of such an air separation plant, in particular at a relatively low or even lower pressure level.

Alternatively, compression of the first amount of air to at least partial liquefaction in the evaporator condenser can also be performed to a pressure level above the first pressure level. In this case, the gaseous third fluid is removed from the air separation unit or from the cooling chamber of the respective air separation unit, in particular at a pressure level that is greater than 320 kPa (3.2 bar). This last-mentioned pressure level may be lower than or near the first pressure level. The first pressure level corresponds to the pressure level of the high pressure column, which operates, in particular, at about 500-700 kPa (5.0-7.0 bar). The pressure level to which the first amount of air is compressed in this case may in particular be 100 kPa to 700 kPa (1 to 7 bar) higher than the first pressure level, for example 600 kPa to 1.4 MPa (6 to 14 bar). Appropriate compression can also be carried out in the main air compressor, for example, if this provides an appropriate final pressure. In such a case, it is also possible to remove other air streams from the main air compressor at a lower pressure level. It is also possible to remove the first amount of air from the main air compressor at a lower pressure level and then bring the specified amount of air to a pressure level above the first pressure level using one or more auxiliary compressors or subsequent compressors. Here, the gaseous third fluid can be removed from the mass transfer column or from the air separation unit or from its cooling chamber, in particular at a pressure level that is from 350 kPa to 1.1 MPa or from 400 kPa to 800 kPa (from 3.5 bar up to 11 bar or 4 to 8 bar) (excluding pressure losses in the heat exchanger and in the pipelines). Alternatively, it is also possible to compress the first amount of air to at least partially liquefy in the evaporator condenser to a pressure level below the first pressure level.

In the method of the invention, the previously compressed and thus cooled amount of air, here referred to as "second" amount of air for simplified or linguistic reference only, is advantageously expanded to a second pressure level and fed into the low pressure column. In this case, said amount of air is the amount of air that is expanded in the turboexpander (Lachmann turbine, injection turbine) and which significantly affects the amount of pressurized nitrogen or liquid product that can be removed from the plant as a whole. The amount of liquid air product(s) removed in each case is discussed below. This amount is in each case expressed as an equivalent amount of liquid nitrogen, the latter being calculated from 1.08 times the amount of liquid oxygen removed plus the amount of liquid nitrogen removed. The equivalent amount of liquid nitrogen is expressed in standard cubic meters per hour.

In the first alternative, in this case, the compression of the second amount of air until it is cooled and expanded to the second pressure level is carried out to a pressure level that is higher than the first pressure level, in particular 100 kPa - 1.1 MPa (1-11 bar) higher than the first pressure level, for example, is from 600 kPa to 1.8 MPa (from 6 to 18 bar), where one or more liquid air products are removed from the air separation unit in an equivalent amount of liquid nitrogen, which corresponds to 3.5 mol. % of the amount of substance supplied in general to the distillation column system, and which corresponds, in particular, to more than 1.5 mol. % of the amount of substance fed in total to the distillation column system. Here, the pressurized nitrogen-rich product(s) is formed using the fluid removed from the pressure column. In this configuration of the present invention, a relatively large amount of suitable products can be provided in this way. The compression of the second amount of air to a pressure level higher than the first pressure level can in this case be carried out in a similar way in the main air compressor, if the latter provides an appropriate final pressure. In this case, additional air streams, for example, the first amount of air, can be removed from the respective main air compressor at a suitably equal or lower pressure level. It is also possible to first compress in the main air compressor to a lower pressure level, where it can then be subsequently compressed in one or more auxiliary compressors or respective subsequent compressors.

On the contrary, in the second alternative, the compression of the second amount of air until it is cooled and expanded to the second pressure level is performed only up to the first pressure level, where one or more liquid air products are removed from the air separation unit in an equivalent amount of liquid nitrogen, which corresponds to up to 1.7 mol. % of the amount of substance supplied in general to the distillation column system, and which corresponds, in particular, to more than 0.7 mol. % of the amount of substance fed in total to the distillation column system. In this configuration of the present invention, fewer corresponding products can be provided in this way than above. The compression can be carried out in any desired manner, in particular in the main air compressor. Additional air fractions, in particular the first air fraction, can then be compressed to the same pressure level or a higher pressure level.

Finally, within the scope of the present invention, it is also possible in a third alternative to compress the second amount of air before cooling it and expanding it to a second pressure level, carried out to a pressure level that is lower than the first pressure level, where one or more liquid air products are removed from the air separation unit in an equivalent amount of liquid nitrogen, which corresponds to up to 1.0 mol. % of the amount of substance supplied in general to the distillation column system, and which corresponds, in particular, (excluding the number of safety washings) to more than 0.0 mol. % of the amount of substance fed in total to the distillation column system. This configuration of the present invention is therefore suitable for those cases in which it is intended to provide an extremely small amount of relevant products. The compression can be carried out here, in particular, in the main air compressor, from which in this case the second amount of air can be removed, in particular at an intermediate pressure level. Here, this is particularly advantageous in terms of energy if the subsequent air compression is still carried out before air purification. Here, the air purification should consist of two adsorbers operating at different pressures (known from WO 2013/053425 A2). In particular, if the compression of the second amount of air before it is cooled and expanded to the second pressure level is carried out to a pressure level that is lower than the first pressure level, it is possible to correspondingly compress the first amount of air to at least partially liquefy in the evaporator condenser to a pressure level below the first pressure level. pressure level. The respective pressure levels below the first pressure level may in this case in particular be equal to each other.

In all the cases explained, it is therefore possible to adapt the configuration of the process according to the invention in each case to the required pressure of the gaseous third fluid which is removed from the mass transfer column or from the air separation plant or from its chiller, in other words the pressurized oxygen rich product, and in each case for the required amount of one or more nitrogen-rich pressurized products and/or one or more liquid products. In this case, it is generally possible to compress the first quantity of air, in other words the quantity of air which is then at least partially liquefied in the condenser-evaporator of the mass transfer column, to a first pressure level or to a higher or lower pressure level (the latter in particular in the case where at least partially liquefied air is supplied to the low-pressure column and in the case of relatively low product pressures) and the compression of the second amount of air, in other words the amount of air which is subsequently subsequently expanded, in particular in the turboexpander, and is fed into the low pressure column to a pressure level that is higher, at or below the first pressure level. Conversely, the additional air which is fed into the pressure column after passing through the main heat exchanger and which is upstream of the main heat exchanger and upstream of the pressure column is not subjected to additional pressure and/or temperature influencing means, is advantageously compressed to a first pressure level upstream of the main heat exchanger. Depending on the pressure level achieved, the main air compressor is used alone or a combination of the main air compressor and one or more auxiliary compressors and/or subsequent compressors is used.

In another configuration of the present invention, it is also possible to expand the corresponding previously compressed and cooled second amount of air to a first pressure level and feed it into a high pressure column, in which the compression of the second amount of air until it is cooled and expanded to the first pressure level is in this case carried out to a pressure level , which is higher than the first pressure level and, in addition, one or more nitrogen-rich gas products under pressure in this case are removed from the air separation unit in a total amount that corresponds to up to 30 mol. % of the amount of substance fed in total to the distillation column system.

According to the present invention, a liquid fifth fluid with a fifth oxygen content, between the third and fourth oxygen content, is removed from the mass transfer column and at least partially fed into the low pressure column. The fifth fluid is removed from the mass transfer column between the first fluid feed point and the oxygen-enriched liquid feed point. According to the invention, the fifth fluid or fraction thereof supplied to the low pressure column is fed into the low pressure column at a position which is below the position at which the fourth fluid or fraction thereof supplied to the low pressure column is fed into the low pressure column. These two positions are advantageously one or more separation areas or separation sections separated from each other. If the mass transfer column has a total number of theoretical or practical trays from 5 to 40, the fifth fluid removal point may be located, in particular, 10 to 30 theoretical or practical trays above the bottom of the mass transfer column. As mentioned, the mass transfer column may in this case contain an additional separation section. According to a particularly preferred embodiment of the present invention, the mass transfer column therefore comprises a first and a second separation section, which in particular each contain mass transfer structures of a suitable type, in particular in the form of separation plates (sieve plates) or in the form of structured or unstructured packings. A liquid collection structure, in particular in the form of a so-called cup, with which the fifth fluid can be collected and discharged, is located between the first and second separation sections. The area, which does not contain mass transfer structures of the type shown, is located in particular between the first and second separation sections.

Removal of the fifth fluid from the mass transfer column and feeding it into the low pressure column, which can also be equipped with a suitable additional separation section for this purpose, results not only in better optimized liquid/vapor (L/V) ratios in the low pressure column, but also to achieve improved mass transfer in the mass transfer column as the concentration profile in the lower region of the column becomes closer to the equilibrium line. As a result, the pressure of the oxygen-rich air product can be increased without the need to simultaneously increase the corresponding air pressure. The main reason for this is that the liquid flowing down in the lower section of the mass transfer column contains significantly less oxygen (the liquid thus becomes colder) and there is less loss when the two liquids are mixed.

In addition, the present invention proposes the use of a so-called forced flow evaporator condenser (particularly in a so-called "co-current" configuration) as an evaporator condenser for evaporating the oxygen-enriched liquid removed from the high pressure column and the bottom liquid of the mass transfer column .

In the pressurized flow condenser-evaporator, the liquid flow is carried under pressure through the evaporation zone by means of its own pressure and partially evaporated in it. Said pressure is generated, for example, by means of a liquid column in the supply line to the evaporation zone and thus purely hydrostatically. Here, the height of said liquid column corresponds to the pressure loss in the evaporation zone. The mixture of gas and liquid leaving the evaporation zone, phase-separated in a "co-current" condenser-evaporator of the type indicated, is carried directly further to the next stage of the process or to a device located downstream and, in particular, is not introduced into the liquid bath of the condenser - evaporator, from which the fraction remaining in liquid form must be recovered again.

In the method according to the invention, the evaporator condenser is therefore designed such that, in said evaporator condenser, a liquid stream containing at least a portion of the oxygen-enriched liquid removed from the pressure column and at least a portion of the bottom liquid from the mass transfer column is carried under pressure through the zone evaporation by means of its own pressure, in particular purely hydrostatically, in other words without additional pressurization by means of a pump (but possibly at a certain hydrostatic pressure or the general main pressure at which the fluid flow is provided, in particular the working pressure explained above above atmospheric column of mass transfer) and partially evaporated in it, where, in particular, prevent re-flow through the evaporation zone of the fraction not evaporated during partial evaporation.

The use of suitable pressure flow evaporator condensers ensures that the pressure of the oxygen product obtained in the form of the third fluid in the respective plant is set to a level significantly higher than in the case of conventional evaporator condenser designs (so-called "pool" evaporator condensers). Within the scope of the present invention, the use of the types of evaporator condensers explained is acceptable due to the large excess of liquid and the relatively low oxygen content.

Within the scope of the present invention, the first fluid may be formed using the bottom liquid from the low pressure column. Conversely, according to another configuration, the first fluid is formed using liquid that is removed from the low pressure column several theoretical or practical trays above the bottom, where additional liquid is removed from the bottom of the low pressure column and discharged from the air separation unit. In this way, it is also possible to provide pure oxygen product in the form of additional liquid removed from the low pressure column.

Within the scope of the present invention, as mentioned, pressurized air is in particular injected into the low pressure column. As mentioned, this contributes to the injection equivalent. Therefore, its amount can be increased compared to known air separation plants containing mixing columns. In the method according to the corresponding configuration of the present invention, it is thus possible to expand the compressed and cooled air to the second pressure level by means of one or more turbo-expanders and feed into the low pressure column. Here, the air can be compressed to the first pressure level, in other words to the pressure level of the high pressure column, as well as to a higher or lower pressure level, as already explained above with reference to the second amount of air. For compression here, in particular, the main air compressor of the air separation plant is used, or said main air compressor is included in the compression together with additional compressors or auxiliary compressors. Cooling is carried out, in particular, in the main heat exchanger. Before and/or during the expansion, the respective air fraction can be cooled, in particular in the main heat exchanger of the air separation plant. The expansion can be carried out, for example, using a generator turbine. Alternatively, it is also possible to carry out the expansion in a turbine which is connected to an auxiliary compressor and which brings the additional air fraction to an even higher pressure level. Said additional air fraction can, in particular, be cooled down before being further compressed or fed into the auxiliary compressor in a warm state. In addition, or as an alternative to using a suitable auxiliary compressor, it is possible to use a separate subsequent compressor which brings the air fraction to a pressure level higher than the first pressure level.

As explained, within the framework of the present invention, it is possible to load the mass transfer column, in particular, with bottom liquid from the high pressure column. However, it is also possible to remove the (additional) bottom liquid from the high pressure column and, without feeding it to the mass transfer column, feed it directly, in other words unchanged in composition, to the low pressure column. This corresponds to the normal operation of the air separation unit.

In another configuration of the process of the invention, the nitrogen-rich or nitrogen-rich fluid may be removed in gaseous form from the pressure column and then expanded with one or more turbo expanders. Thus, so-called pressurized nitrogen turbines can be used, as explained in the introduction. In particular, it is also possible to use so-called pressurized nitrogen turbines with impurities. Accordingly, the expanded fluids may be fed into the low pressure column or discharged from the air separation unit. Such fluids contribute to the injection equivalent.

The present invention also extends to an air separation plant comprising a distillation column system which comprises a high pressure column configured to operate at a first pressure level, a low pressure column configured to operate at a second pressure level below the first pressure level, and a mass transfer column configured to for operation at a third pressure level, where the air separation unit is designed to carry out mass transfer in the mass exchange column of a liquid first fluid with a first oxygen content and a gaseous second fluid with a second oxygen content, below the first oxygen content, with each other, to remove the gaseous third fluid media with a third oxygen content reduced relative to the first oxygen content from the mass transfer column and at least partial unloading of said third fluid from the air separation unit to remove a liquid fourth fluid with a fourth oxygen content corresponding to at least a second oxygen content from the additional mass transfer column and for at least partially supplying said fourth fluid to the low pressure column and for generating a first fluid using at least a portion of the oxygen rich liquid removed from the low pressure column. The air separation unit is also configured to generate a second fluid using the oxygen-enriched liquid removed from the high pressure column. Moreover, the air separation unit is designed to mix and partially vaporize in the evaporator condenser the oxygen-enriched liquid removed from the high pressure column and the bottom liquid of the mass transfer column.

In this case, an evaporator condenser is constructed in the air separation plant of the invention and included in the air separation plant such that a liquid stream that contains at least a portion of the oxygen-enriched liquid removed from the pressure column and at least a portion of the bottom liquid from the mass transfer column, is carried under pressure through the evaporation zone using its own pressure and partially evaporated in it.

Moreover, according to the invention, the air separation plant is designed to remove a liquid fifth fluid with a fifth oxygen content, between the third and fourth oxygen content, from the mass transfer column between the first fluid supply point and the oxygen-enriched liquid supply point, and to at least partially supply said the fifth fluid into the low pressure column, in which means are provided that are made for supplying the fifth fluid or its fraction supplied to the low pressure column below the fourth fluid or its fraction supplied to the low pressure column. Appropriate means are provided for removing and supplying fluid streams according to the invention, for example, connecting pipelines and the like.

For the features and advantages of an appropriate air separation plant, reference should be made explicitly to the above explanations in relation to the method of the invention and its various advantageous configurations. The corresponding air separation plant is in particular designed for the practical implementation of the corresponding method and contains the corresponding means.

In the air separation plant according to the invention, the high pressure column and the low pressure column, in particular, are connected to each other in a heat exchange manner by means of a multi-stage cascade or falling film evaporator.

The invention is explained in more detail with reference to the accompanying drawings, which show preferred embodiments of the invention.

Brief description of the drawings

On FIG. 1 shows an air separation plant according to one embodiment of the invention in the form of a simplified process flow diagram.

On FIG. 1 shows an air separation plant according to one embodiment of the invention in the form of a simplified process flow diagram.

On FIG. 1 shows an air separation plant according to one embodiment of the invention in the form of a simplified process flow diagram.

On FIG. 2 shows an air separation plant according to one embodiment of the invention in the form of a simplified process flow diagram.

On FIG. 3 shows an air separation plant according to one embodiment of the invention in the form of a simplified process flow diagram.

On FIG. 4 shows an air separation plant according to one embodiment of the invention in the form of a simplified process flow diagram.

On FIG. 5A shows an air separation plant according to one embodiment of the invention in the form of a simplified process flow diagram.

On FIG. 5B shows an air separation plant according to one embodiment of the invention in the form of a simplified process flow diagram.

On FIG. 5C shows an air separation plant according to one embodiment of the invention in the form of a simplified process flow diagram.

On FIG. 6 shows an air separation plant according to one embodiment of the invention in the form of a simplified process flow diagram.

On FIG. 7 shows an air separation plant according to one embodiment of the invention in the form of a simplified process flow diagram.

On FIG. 8 shows an air separation plant according to one embodiment of the invention in the form of a simplified process flow diagram.

On FIG. 9 shows an air separation plant according to one embodiment of the invention in the form of a simplified process flow diagram.

Detailed description of the invention

In the drawings, elements that correspond structurally or functionally to each other are identified by the same reference numerals and, for the sake of clarity, are not explained again. Air separation plants according to the preferred embodiments of the present invention are shown in each case on the basis of the drawings. However, the corresponding explanations apply in the same way to the methods according to the preferred configurations of the present invention, so that when the details or the corresponding settings are described below, the corresponding explanations for the method steps performed by said details are also applicable. In the drawings, liquid material flows are each shown with filled (black) arrows and gaseous material flows are each shown with empty (white) arrows.

In the description of the drawings, the apparatus referred to above as "mass transfer column" is simply referred to as "mixing column". As explained, it differs from a conventional mixing tower in a number of ways.

On FIG. 1, an air separation plant according to one embodiment of the present invention is shown in the form of a highly simplified process flow diagram and is generally labeled 100.

In the air separation unit 100, atmospheric air (AIR) is sucked in through the filter 2 by means of a conventionally multi-stage air compressor 1 and supplied as the supply air stream a to the cooler 3. After being cooled there, the supply air stream a is purified in the adsorption unit 4, in particular, free from water and carbon dioxide. If required, a portion of the air from the purified supply air stream, which is still labeled a, is further compressed and used to supply the required air to any consumers (Cust Air).

In the air separation unit 100, the fraction of the feed air stream a, in the form of the so-called injection stream b, is first cooled to an intermediate temperature level in the main heat exchanger 5 of the air separation unit 100, expanded in a turbo-expander 6 (Lachmann turbine) which is connected to a generator G, and is fed to the low pressure column 12 of the distillation column system 10, which also includes a high pressure column 11 and a mixing column 13.

In the air separation unit 100, an additional fraction of the feed air stream a, in the form of a stream c of the substance, is cooled to the final temperature level in the main heat exchanger 5 of the air separation unit 100 and then separated, still in a gaseous state, into two partial streams d and e.

The partial stream d is liquefied in a condenser-evaporator 7, the latter in the example shown being located in the lower region of the mixing column 13 and, as explained above, constructed in the form of a pressure-flow condenser-evaporator, passed through a countercurrent subcooler 8 and expanded into a low pressure column 12 . The partial flow e is fed into the lower region of the high pressure column 11 .

The oxygen-enriched liquid is withdrawn in the form of a stream f of matter from the bottom of the high pressure column 11 and expanded into the lower region of the mass transfer region in the mixing column 13. This stream is thus used in place of the feed air stream which is normally supplied to the mixing column 13. In the mixing column 13, in particular in the condenser-evaporator 7, the evaporating liquid is passed in countercurrent to the flow g of the substance, the latter being introduced in liquid form into the upper region of the mass transfer region in the mixing column 13.

To form a flow g of the substance, the oxygen-enriched liquid is removed from the bottom of the low pressure column 12, pressurized with a pump 9, passed through a counterflow subcooler 8 and heated to an intermediate temperature level in the main heat exchanger 5. Additional oxygen-enriched liquid removed from the bottom of the column 12 low pressure and pressurized by the pump 9 can be discharged from the air separation unit 100 as a liquid oxygen product (LOX).

The gas mixture withdrawn from the top of the mass transfer region of the mixing column 13 in the form of a material stream h is fully heated in the main heat exchanger 5, expanded and provided as an oxygen product gas (GOX) at a pressure level of, for example, approximately 320 kPa abs. (3.2 bar abs).

The liquid from the bottom of the mass transfer region of the mixing column 13 is partially evaporated in the condenser-evaporator 7. In this case, the condenser-evaporator 7 is supplied with a liquid stream in the form of a liquid from the bottom of the mass transfer region of the mixing column 13, which contains at least a portion of the oxygen-enriched liquid removed from column 11 high pressure, and at least part of the bottom liquid from the column 13 mass transfer. The liquid flow is carried out under pressure through the evaporation zone of the condenser-evaporator 7 using its own pressure and partially evaporated in it. The evaporated fraction rises to the mass transfer area, and the non-evaporated fraction, together with the liquid flowing down in the mixing column 13, is recovered in the form of a stream i of the substance. Stream i of the substance is carried out through a counter-current supercooler 8 and expanded into the Central region of the column 12 low pressure.

In the example shown, the mixing column 13 has two separating sections. The liquid material stream p is withdrawn from the intermediate region of the mixing column 13 and, in particular, as shown, is supercooled and fed into the low pressure column 12, the latter also being able to be provided with an additional separation section. The liquid fifth fluid is then removed in the form of a substance stream p from the mass transfer column 13 between the feed points of the substance streams f and g and at least partially fed into the low pressure column 12. The low-pressure column 12 is fed here below the material flow i.

The nitrogen-rich gas from the top of the high pressure column 11 is recovered in the form of a stream to matter from the high pressure column 11 . A part of it, in the form of material stream 1, is heated in the main heat exchanger 5 and, after possible further compression, provided in the form of a pressurized nitrogen product gas (PGAN) and/or used as seal gas.

The other part of the nitrogen-rich gas recovered in the form of a stream to the substance from the top of the high pressure column 11 is liquefied in the main condenser 14, which connects the high pressure column 11 and the low pressure column 12 with heat exchange, and is partially recycled as a return flow to the column 11 high pressure and partly (see index A) is provided as a liquid nitrogen product (LIN). The main condenser 14 may in particular be in the form of a multi-level cascaded evaporator, as described, for example, in DE 102010051526 A1.

In addition, the liquid nitrogen-enriched substance mixture is recovered in the form of a substance stream m from the intermediate region of the high pressure column 11, passed through a countercurrent subcooler 8 and expanded into the low pressure column 12.

The so-called nitrogen with impurities is removed in the form of a stream n of substance from the top of the low pressure column and passed through a counter-current subcooler 8. After being divided into two partial streams and heated in the main heat exchanger 5, this nitrogen with impurities can be used as regeneration gas or cooling gas in the cooler 3 or in adsorption unit 4.

On FIG. 2 shows an air separation plant according to another embodiment of the present invention in the form of a highly simplified process flow diagram, and is generally designated 200.

The air separation unit 200 shown in FIG. 2 is different from the air separation unit 100 shown in FIG. 1, mainly in that the partial flow b of the supply air is further cooled here in the main heat exchanger 5 after it has been expanded in the turboexpander 6.

On FIG. 3 shows an air separation plant according to another embodiment of the present invention in the form of a highly simplified process flow diagram, and is designated generically 300.

The air separation unit 300 shown in FIG. 3 is different from the air separation unit 100 shown in FIG. 1, mainly in that a partial feed air flow b is here compressed in an auxiliary compressor 21, which is mechanically connected to the turboexpander 6, before being cooled to an intermediate temperature level in the main heat exchanger 5. In this way, a reduction in the injection quantity can be realized with an increased removal of the gaseous nitrogen product under pressure (PGAN).

On FIG. 4 shows an air separation plant according to another embodiment of the present invention in the form of a highly simplified process flow diagram, and is generally designated 400.

The air separation unit 400 shown in FIG. 4 is different from the air separation unit 100 shown in FIG. 1, mainly in that the partial stream from the feed air is not divided into two partial streams d and e. Instead, in this case, the entire partial stream c is partially condensed in the evaporator condenser 7 and fed into the high pressure column 11. This makes it possible to provide the gaseous oxygen product (GOX) at a higher pressure level, namely at a pressure level of, for example, up to about 400 kPa abs. (4.0 bar abs.) with a temperature difference in the condenser 14 of approximately 1K.

On FIG. 5A shows an air separation plant according to another embodiment of the present invention in the form of a highly simplified process flow diagram, and is designated generically 500.

The air separation unit 500 shown in FIG. 5A is different from the air separation unit 100 shown in FIG. 1, mainly in that a post-compressor 51 is used. Said post-compressor can be designed, in particular together with the main air compressor 1, in the form of one multi-stage mechanism, from which the partial flow b is removed at an intermediate pressure. It additionally compresses the partial supply air flow, which corresponds to the partial flow d and is also referred to here as d. This also makes it possible to provide the gaseous oxygen product (GOX) at a higher pressure level.

As further shown in FIG. 5A, here the air liquefied in the evaporator condenser 7 of the mixing column 13 is also partly (see pointer B) fed into the high pressure column 11.

On FIG. 5B shows an air separation plant according to another embodiment of the present invention in the form of a highly simplified process flow diagram, and is generally designated 510. The air separation plant 510 constitutes a variation of the air separation plant 500 of FIG. 5A.

The air separation unit 510 shown in FIG. 5B differs from the air separation unit 500 shown in FIG. 5A, mainly in that two subsequent compressors 52 and 53 are used instead of the subsequent compressor 51. These two subsequent compressors can also be designed, together with the main air compressor 1, in the form of one multi-stage mechanism, from which the partial flow b is removed at an intermediate pressure. Here, first, the subsequent compressor 52 compresses an amount of air that corresponds to the sum of the partial flows, also denoted c and d. Partial stream c is cooled at an appropriate pressure level, which is achieved by compression in the subsequent compressor 52. Partial stream d is further compressed in the subsequent compressor 53 and then cooled. The air separation unit 510 shown in FIG. 5B provides in particular a relatively low production of liquid or production of pressurized nitrogen product gas (PGAN), with the result that the injection stream, ie partial stream b, is compressed to a relatively low pressure level.

The feed air for the high pressure column 11, ie the partial flow c, is compressed to its pressure level. In the air separation unit 510 shown in FIG. 5B also provide a gaseous oxygen product (GOX) at a higher pressure level. Therefore, the air of the partial flow d is additionally compressed accordingly.

On FIG. 5C shows an air separation plant according to another embodiment of the present invention in the form of a highly simplified process flow diagram, and is generally designated 520. Air separation plant 520 constitutes another embodiment of air separation plant 500 according to FIG. 5A.

The air separation unit 520 shown in FIG. 5C differs from the air separation unit 500 shown in FIG. 5A, mainly in that a subsequent compressor 54 is used instead of the subsequent compressor 51. The latter can also be designed, together with the main air compressor 1, in the form of one multi-stage mechanism, from which, however, in this case then a partial supply air flow, which corresponds to partial flow c, removed at intermediate pressure. The subsequent compressor 54 compresses an amount of air that corresponds to the sum of the partial flows, also referred to here as b and d. Partial streams b and d are cooled at the appropriate pressure level, which they achieve by compression in the subsequent compressor 54.

The air separation unit 520 shown in FIG. 5C is provided in particular for relatively high liquid production or pressurized nitrogen product gas (PGAN) production. The gaseous oxygen product (GOX) is then produced at a higher pressure and for this reason the usual post-compression of the partial streams b and d is carried out. The turbo expander 6 is designed to contain an auxiliary compressor stage.

On FIG. 6 shows an air separation plant according to another embodiment of the present invention in the form of a highly simplified process flow diagram and is designated generically 600.

The air separation unit 600 shown in FIG. 6 is different from the air separation unit 500 shown in FIG. 5, mainly in that a subsequent compressor 61 is used which further compresses the partial supply air flow, which corresponds to partial flow c, here also designated c, and which further compresses the partial supply air flow, which corresponds to partial flow d, here also designated d. . In this configuration also the main air compressor 1 and the subsequent compressor 61 can in particular be constructed in the form of one multi-stage mechanism from which the partial flow b is removed at an intermediate pressure.

The air separation unit 600 shown in FIG. 6 is particularly suitable if a small amount of liquid products or a pressurized gas nitrogen product (PGAN) is produced, and in the case of an oxygen product pressure that is comparable to the pressure in the air separation unit 100 according to FIG. 1. The turbine amount, that is, the amount of air expanded in the turbo expander 6, is large in this case, but the cooling capacity is relatively low because the pressure gradient in the turbo expander is relatively low. In this case, relatively large (main) heat exchangers are sometimes also needed, however, the efficiency remains very high, since the turbine quantity is not compressed at the same time to the final pressure.

On FIG. 7 shows an air separation plant according to another embodiment of the present invention in the form of a highly simplified process flow diagram, and is generally designated 700.

The air separation unit 700 shown in FIG. 7 is different from the air separation unit 500 shown in FIG. 5, mainly in that a subsequent compressor 71 is used, which, however, further compresses only a partial supply air flow, which corresponds to partial flow c and is also denoted c here. This configuration is particularly suitable for applications where, in addition to producing a small amount of liquid products or a small amount of pressurized gas nitrogen product (PGAN), it is intended to produce a gaseous oxygen product (GOX) at a pressure level of less than about 320 kPa abs. (3.2 bar abs).

On FIG. 8 shows an air separation plant according to another embodiment of the present invention in the form of a highly simplified process flow diagram, and is designated generically 800.

The air separation unit 800 shown in FIG. 8 is different from the air separation unit 100 shown in FIG. 1, mainly in that a cold auxiliary compressor 81 is used, which further compresses the partial supply air flow, which corresponds to the partial flow d, also referred to here as d, and which was previously cooled in the main heat exchanger 5.

In the configuration of the air separation unit 800 according to FIG. 8, only one pressure level dominates the main heat exchanger (or only one compressor is used), however, a higher oxygen product pressure is obtained. Pressurization of the air stream d condensed in the evaporator condenser 7 of the mixing column 13 is carried out by means of a cold auxiliary compressor 81. In this case, the (main) heat exchanger 5 is a relatively large structure and the excess cooling capacity is practically converted into a higher pressure. The advantage is that no additional compressor device or compressor stage has to be used. The device, consisting of a turboexpander 6 and a cold auxiliary compressor 81, can be additionally connected to a generator or an oil brake.

As further shown in FIG. 8, here, as in the configuration of FIG. 5, the air liquefied in the evaporator condenser 7 of the mixing column 13 is also partly fed (see pointer B) to the high pressure column 11.

On FIG. 9 shows an air separation plant according to another embodiment of the present invention in the form of a highly simplified process flow diagram, and is designated generically 900.

The air separation unit 900 shown in FIG. 9 is different from the air separation unit 100 shown in FIG. 1, mainly in that a flow g of matter is formed by using liquid which is removed above the bottom of the low pressure column 12. Here, pure oxygen with an oxygen content of approximately 99.5% is removed in the form of an o-substance stream from the bottom of the low pressure column 12 and provided as a liquid oxygen product (LOX). In particular, the flow of substances can be carried out through a counter-current supercooler 8.

Claims (23)

1. A method for cryogenic air separation using an air separation unit (100-900) containing a system (10) of distillation columns, which contains a high pressure column (11) operating at a first pressure level, a low pressure column (12) operating at a second pressure level below the first pressure level, and a mass transfer column (13) operating at a third pressure level, where in the mass transfer column (13) a liquid first fluid with a first oxygen content and a gaseous second fluid with a second oxygen content below the first oxygen content , are subjected to mass exchange with each other, the gaseous third fluid with a third oxygen content reduced in relation to the first oxygen content is removed from the mass transfer column (13) and at least partially unloaded from the air separation unit (100-900), the liquid fourth fluid the medium with a fourth oxygen content corresponding to at least a second oxygen content is removed and from the mass transfer column (13) and at least partially fed into the low pressure column (12), the first fluid is formed using at least a portion of the oxygen-rich liquid removed from the low pressure column (12), the gaseous second fluid is formed using the oxygen-enriched liquid removed from the high pressure column (11) and the oxygen-enriched liquid removed from the high pressure column (11) and the bottom liquid of the mass transfer column (13) are mixed and partially evaporated using an evaporator condenser (7), characterized in that , what the liquid stream, which contains at least part of the oxygen-enriched liquid removed from the high pressure column (11) and at least part of the bottom liquid from the mass transfer column (13), is carried out in the evaporator condenser (7) under pressure through the evaporation zone using its own pressure and partially evaporate in it, liquid fifth fluid with a fifth oxygen content, between the third and fourth oxygen content, is removed from the mass transfer column (13) between the first fluid feed point and the oxygen-enriched liquid feed point, and is at least partially fed into the low pressure column (12), and the fifth fluid or its fraction supplied to the low pressure column (12) is fed to the low pressure column (12) below the fourth fluid or its fraction supplied to the low pressure column (12). 2. The method according to claim 1, in which the previously compressed and cooled first amount of air is further cooled and at least partially liquefied in the condenser-evaporator (7), where the cooled and at least partially liquefied first amount of air is then at least partially supplied into the system (10) of distillation columns. 3. The method according to claim 2, in which the compression of the first amount of air before at least partial liquefaction in the condenser-evaporator (7) is carried out to a first pressure level, to a pressure level above the first pressure level, or to a pressure level below the first pressure level. 4. The method according to any one of paragraphs. 2 and 3, in which the previously compressed and cooled second amount of air is expanded to a second pressure level and fed into the low pressure column (12). 5. The method of claim. 4, in which the compression of the second amount of air before cooling and expanding it to the second pressure level perform up to a pressure level above the first pressure level, where one or more liquid air products are removed from the air separation unit (100-900) in an equivalent amount of liquid nitrogen, which corresponds to up to 3.5 mol. % of the amount of substance fed in total to the system (10) distillation columns, or perform up to the first pressure level, where one or more liquid air products are removed from the air separation unit (100-900) in an equivalent amount of liquid nitrogen, which corresponds to up to 1.7 mol. % of the amount of substance fed in total to the system (10) distillation columns, or perform to a pressure level below the first pressure level, where one or more liquid air products are removed from the air separation unit (100-900) in an equivalent amount of liquid nitrogen, which corresponds to up to 1.0 mol. % of the amount of substance supplied in total to the system (10) of distillation columns, where the equivalent amount of liquid nitrogen in each case is determined based on 1.08 times the amount of liquid oxygen removed plus the amount of liquid nitrogen removed. 6. The method according to one of paragraphs. 2 or 3, in which the previously compressed and cooled second amount of air is expanded to the first pressure level and fed into the high pressure column (11), wherein the compression of the second amount of air before it is cooled and expanded to the first pressure level is performed to a pressure level, which above the first pressure level, and one or more nitrogen-rich compressed gas products are removed from the air separation unit (100-900) in a total amount that corresponds to up to 30 mol. % of the amount of substance fed in total to the system (10) distillation columns. 7. The method according to one of the preceding claims, in which the fractions of the liquid stream, which contains at least a part of the oxygen-enriched liquid removed from the high pressure column (11), and at least a part of the bottom liquid from the mass transfer column (13), which is not evaporated during partial evaporation in the condenser-evaporator (7), do not allow to flow again through the evaporation zone. 8. The method according to one of the preceding claims, wherein the first fluid is formed using bottom fluid from the low pressure column (12). 9. The method according to one of paragraphs. 1-7, in which the first fluid is formed using liquid that is removed from the low pressure column (12) several theoretical or practical plates above the bottom, where additional liquid is removed from the bottom of the low pressure column (12) and unloaded from the installation (100 -900) air separation. 10. The method according to one of the preceding claims, wherein the bottom liquid is removed from the high pressure column (11) and fed unchanged in the composition of the substance into the low pressure column. 11. A process according to one of the preceding claims, wherein the nitrogen-rich or nitrogen-rich fluid is removed in gaseous form from the high pressure column (11) and then expanded by one or more turbo-expanders. 12. Air separation unit (100-900) containing a system (10) of distillation columns, which contains a high pressure column (11) designed to operate at a first pressure level, a low pressure column (12) configured to operate at a second pressure level , below the first pressure level, and a mass transfer column (13) designed to operate at a third pressure level, where the air separation unit (100-900) is made to carry out, in the mass transfer column (13), mass transfer of the liquid first fluid with the first oxygen content and a gaseous second fluid with a second oxygen content, below the first oxygen content, with each other to remove a gaseous third fluid with a third oxygen content, reduced in relation to the first oxygen content, from the mass transfer column (13) and at least partially unload the specified third fluid from the installation (100-900) air separation, to remove the liquid fourth fluid with the fourth soda an oxygen content corresponding to at least a second oxygen content from the additional mass transfer column (13) and for at least partial supply of said fourth fluid to the low pressure column (12) to form a first fluid using at least a portion of the oxygen-rich the liquid removed from the low pressure column (12) to form a second fluid using the oxygen-enriched liquid removed from the high pressure column (11) and for mixing and for partial evaporation using the oxygen-enriched liquid condenser-evaporator (7), removed from the high pressure column (11) and the bottom liquid of the mass transfer column (13), characterized in that the condenser-evaporator (7) is designed and included in the air separation unit so that the liquid stream, which contains at least a part of the oxygen-enriched liquid removed from the high pressure column (11), and at least a part of the bottom liquid from the mass transfer column (13) , is carried under pressure through the evaporation zone with the help of its own pressure and partially evaporated in it, means are provided that are designed to remove the liquid fifth fluid with the fifth oxygen content, between the third and fourth oxygen contents, from the mass transfer column (13) between the first fluid supply point and the oxygen-enriched liquid supply point, and for at least partial supply of said the fifth fluid into the low pressure column (12), and means are provided that are made for supplying the fifth fluid or its fraction supplied to the low pressure column (12) to the low pressure column (12) below the fourth fluid or its fraction supplied to the low pressure column (12). 13. Air separation unit (100-900) according to claim 12, in which the high pressure column (11) and the low pressure column (12) are connected to each other in a heat exchange manner using a multi-level cascade evaporator or using an evaporator (14) with a falling film.

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