Low-purity oxygen production plant

Abstract

The utility model provides a kind of low pure oxygen production equipment.Wherein, second feed pipeline is set to the second part of feed air that is pressurized by main air compressor is sent into the feed position of mixing tower after being expanded by expander.The starting end of bypass pipeline is connected to first feed pipeline, and terminal end is connected to second feed pipeline and between expander and feed position, so that the bypass stream of the first part of feed air is sent to second feed pipeline, so that bypass stream is sent into the feed position of mixing tower together with second part, as the feed gas of mixing tower.First output pipeline is set to export low pure oxygen stream from the top of mixing tower, finally become low pure oxygen product.The above-mentioned low pure oxygen production equipment can produce low pressure low pure oxygen product with low energy consumption.

Description

Technical Field

[0001] This utility model belongs to the field of air separation and relates to a low-purity oxygen production equipment that obtains low-purity oxygen products through air separation. Background Technology

[0002] Air separation units are widely used to separate ambient air at low temperatures to produce high-purity oxygen, nitrogen, argon, etc. Typically, air separation units consist of a high-pressure column and a low-pressure column thermally connected via a main condenser-evaporator.

[0003] For many industrial applications, such as certain combustion or gasification processes, high-purity oxygen is not required. Instead, low-purity oxygen products, such as GOX, are sufficient. The oxygen concentration of low-purity oxygen products is typically between 90% and 98%, for example, 95%.

[0004] To effectively meet this need, some equipment now incorporates mixing towers. For example, such as... Figure 2 As shown, the mixing tower receives a stream of liquid oxygen from the main condenser-evaporator and brings it into contact with an updraft. This updraft consists of a portion of the medium-pressure feed air.

[0005] One drawback of the above process is that the operating pressure of the mixing tower is tied to the pressure of the medium-pressure feed air. Therefore, the low-purity oxygen product also leaves the mixing tower at a relatively high pressure. For users requiring the delivery of low-pressure, low-purity oxygen products, this high-pressure product must be depressurized using a pressure-reducing device. This results in a significant and costly waste of energy, as the compression work invested in producing the high-pressure product is simply dissipated as heat. Another drawback is that the expanded low-pressure feed air is fed into the low-pressure tower, but the amount of low-pressure feed air fed into the low-pressure tower is limited to ensure distillation efficiency, thus limiting the product yield.

[0006] Therefore, design improvements are needed to enable efficient and low-energy production of low-pressure, low-purity oxygen products, or to increase the yield of liquid products. Furthermore, it is possible to produce higher yields of low-purity oxygen products, and even further, the yield of low-purity oxygen products can be adjusted. Utility Model Content

[0007] The purpose of this invention is to provide a low-purity oxygen production equipment that can produce low-pressure, low-purity oxygen products with low energy consumption.

[0008] Another objective of this invention is to provide a low-purity oxygen production equipment that produces a high yield of low-purity oxygen products.

[0009] This invention provides a low-purity oxygen production device that obtains low-purity oxygen product through air separation. The low-purity oxygen production device includes a piping system and a distillation column system. The distillation column system includes a high-pressure column, a low-pressure column, and a mixing column. The high-pressure column and the low-pressure column are thermally connected via a main condenser-evaporator. The piping system includes a first feed line and an oxygen supply line. The first feed line is configured to send a first portion of the feed air, pressurized by the main air compressor, into the high-pressure column for distillation. The oxygen supply line is configured to send liquid oxygen from the evaporation space of the main condenser-evaporator to the oxygen supply position of the mixing column as reflux liquid. The piping system also includes a second feed line, a bypass line, and a first output line. An expander is installed in the second feed line. The second feed line is configured to send a second portion of the feed air, pressurized by the main air compressor, expanded by the expander, into the feed position of the mixing column. The bypass line starts at the first feed line and ends at the second feed line, located between the expander and the feed position. This bypass stream of the first portion of the feed air is delivered to the second feed line, where it, along with the second portion, is fed into the feed position of the mixing tower as feed gas. The mixing tower has a tray positioned between the feed position and the oxygen delivery position along its height. The first output line is configured to exit a stream of low-purity oxygen from the top of the mixing tower, ultimately becoming the low-purity oxygen product.

[0010] In one embodiment, the feed air is pressurized to a first pressure by the main air compressor, and a first portion is sent to the high-pressure tower at the first pressure. A second portion is expanded to a second pressure by an expander, and a second portion is sent to the mixing tower at the second pressure. The second pressure is lower than the first pressure. A pressure-reducing element is installed in the bypass pipeline, and the bypass stream is reduced to the second pressure by the pressure-reducing element before being sent to the second feed pipeline.

[0011] In one embodiment, the pressure-reducing element is a throttle valve configured to adjust the flow rate.

[0012] In one embodiment, a booster and an aftercooler are also provided in the second feed line. The second feed line is configured to sequentially pass a second portion of the feed air through the booster for pressurization, the aftercooler for cooling, and the expander for expansion before sending it into the mixing tower. The expander drives the booster.

[0013] In one embodiment, the low-purity oxygen production equipment also includes a main heat exchanger. The piping system is configured such that the feed air, after being pressurized by the main air compressor, is split into a first portion and a second portion. The first portion, after being completely cooled by the main heat exchanger via a first feed line, enters the high-pressure tower. The second portion, after being pressurized by a booster and cooled by an aftercooler via a second feed line, enters the main heat exchanger for complete cooling, then expands via an expander, and finally enters the mixing tower. The low-purity oxygen stream exiting the top of the mixing tower is completely reheated by the main heat exchanger via a first output line, thus becoming the low-purity oxygen product.

[0014] In one embodiment, the liquid oxygen exits from the evaporation space of the main condenser at a position higher than the oxygen delivery level, allowing the liquid oxygen to directly reach the oxygen delivery level through the head difference.

[0015] In one embodiment, the piping system is further configured to feed the bottom liquid accumulated at the bottom of the mixing tower into the low-pressure tower. The piping system is also configured to feed an intermediate stream drawn from the middle of the mixing tower into the low-pressure tower.

[0016] In one embodiment, the bottom liquid is fed into the first intermediate position of the low-pressure column, and the intermediate stream is fed into the second intermediate position of the low-pressure column, with the first intermediate position being higher than the second intermediate position.

[0017] In one embodiment, the second portion, after being expanded by the expander, is entirely fed into the mixing tower.

[0018] In one embodiment, the oxygen feed point is the high position of the mixing tower above all trays, while the feed point is the low position of the mixing tower below all trays. The first portion is fed into the low position of the high-pressure tower below all trays.

[0019] In the aforementioned low-purity oxygen production equipment, the second portion of the feed air, expanded by the expander, is sent to the mixing tower via a second feed pipeline. This reduces the pressure of the feed stream entering the mixing tower, resulting in a lower pressure low-purity oxygen product that does not require further depressurization. Therefore, this low-purity oxygen production equipment can produce low-pressure low-purity oxygen products with low energy consumption. Furthermore, since the second portion of the feed air expanded by the expander is not sent to the low-pressure tower, the flow rate is not limited by the amount of gas entering the tower, thus not affecting the refrigeration capacity. This also provides flexibility for increasing the production capacity of liquid products.

[0020] Furthermore, by setting up a bypass pipeline, a portion of the feed stream destined for the high-pressure distillation tower—that is, the bypass stream of the first portion of the feed air—is rationally utilized and fed into the mixing tower together with the second portion of the expanded feed air, serving as the upward airflow of the mixing tower. This can increase the yield of low-purity oxygen products, meaning a higher output of low-purity oxygen products can be achieved.

[0021] Furthermore, by installing a pressure-reducing element such as a throttle valve in the bypass pipeline, pressure adaptation can be achieved more easily, and the bypass flow rate can be adjusted, thus allowing for flexible adjustment of the production of low-purity oxygen products. Attached Figure Description

[0022] The advantages and spirit of this utility model can be further understood through the following detailed description and accompanying drawings.

[0023] Figure 1 This is a schematic diagram of an exemplary low-purity oxygen production equipment according to an embodiment of the present utility model.

[0024] Figure 2 This is a schematic diagram of an exemplary low-purity oxygen production equipment based on a comparative example. Detailed Implementation

[0025] The specific embodiments of this utility model are described in detail below with reference to the accompanying drawings. However, it should be understood that this utility model is not limited to the embodiments described below, and the technical concept of this utility model can be implemented in combination with other known technologies or functions, or with other technologies that are the same as those known technologies.

[0026] For example, if the first feature described subsequently in the specification is formed above or on the second feature, this can include embodiments where the first and second features are formed by direct connection, or embodiments where an additional feature is formed between the first and second features, so that the first and second features are not directly connected. Furthermore, when the first element is described in a manner connected or combined with the second element, the description includes embodiments where the first and second elements are directly connected or combined with each other, as well as embodiments where one or more other intervening elements are incorporated to indirectly connect or combine the first and second elements with each other.

[0027] The term "and / or" as used herein includes any and all combinations of one or more of the related listed items. Unless otherwise stated, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood in the art to which this invention pertains. It should also be understood that terms, such as those defined in common dictionaries, should be understood to have the same meaning as they have in the context of this specification and the related art, and should not be interpreted in an idealized or overly formal sense unless expressly stated herein. For the sake of brevity and / or clarity, well-known functions or constructions may not be described in detail.

[0028] Figure 2 A comparative example is shown. Figure 2 In the 10m low-purity oxygen production equipment, the feed air a0 is split into two streams before the main heat exchanger 6: a1 and a2. After being cooled by the main heat exchanger 6, part a10 enters the high-pressure tower 21 for distillation, while the other part a13 enters the mixing tower 23 as an upward flow. The second part a2 is pressurized and cooled by the booster 41 before entering the main heat exchanger 6 for further cooling. It then enters the expander 42 for expansion and finally enters the intermediate position P28 of the low-pressure tower 22.

[0029] Figure 2In the comparative example, the operating pressure of mixing tower 23 is consistent with the first portion a1 of the feed air a0, while the pressure of the first portion a1 of the feed air a0 is determined by high-pressure tower 21. Therefore, the pressure of the low-purity oxygen product Po exiting from the top of mixing tower 23 is also relatively high. For users who need to transport low-pressure low-purity oxygen product Po, this pressure must be reduced using a pressure reducing device. This results in energy waste.

[0030] Furthermore, the second portion a2, after being expanded by expander 42, is fed into low-pressure column 22. The amount of the gaseous second portion a2 fed into low-pressure column 22 must be limited, otherwise it will affect the distillation efficiency and oxygen recovery rate. Therefore, the amount of expansion refrigeration is limited, thus limiting the yield of liquid products.

[0031] Therefore, improvements are needed.

[0032] Figure 1 An exemplary configuration of a low-purity oxygen production apparatus 10 according to the present invention is shown. The low-purity oxygen production apparatus 10 obtains a low-purity oxygen product Po through air separation. Figure 1 and Figure 2 Similar elements are shown with similar reference numerals. It is understood that the accompanying drawings are for illustrative purposes only and are not necessarily drawn to scale, and should not be construed as limiting the scope of protection of this utility model.

[0033] See Figure 1 The low-purity oxygen production equipment 10 includes a piping system 1 and a distillation column system 2. The distillation column system 2 includes a high-pressure column 21, a low-pressure column 22, and a mixing column 23.

[0034] It is understood that the use of "high-pressure column 21" and "low-pressure column 22" here is only to indicate that the two distillation columns operate at different pressures, rather than to specify their exact operating pressure ranges. For example, the operating pressure of high-pressure column 21 is around 5.5 bara, and it is often referred to as a medium-pressure column in engineering. The operating pressure of low-pressure column 22 is around 1.3 bara.

[0035] The high-pressure tower 21 and the low-pressure tower 22 are thermally connected through the main condenser-evaporator 24. That is, the high-pressure tower 21 and the low-pressure tower 22 exchange heat through the main condenser-evaporator 24.

[0036] The piping system 1 includes a first feed line 11 and an oxygen supply line 16. The first feed line 11 is configured to send the first portion a1 of the feed air a0 pressurized by the main air compressor 3 into the high-pressure tower 21 for rectification. The oxygen supply line 16 is configured to send liquid oxygen lo from the evaporation space of the main condenser evaporator 24 into the oxygen supply position P31 of the mixing tower 23 as the reflux liquid of the mixing tower 23.

[0037] The piping system 1 also includes a second feed line 12. An expander 42 is installed in the second feed line 12. The second feed line 12 is configured to send the second part a2 of the feed air a0 pressurized by the main air compressor 3, after being expanded by the expander 42, into the feed position P32 of the mixing tower 23.

[0038] The piping system 1 also includes a bypass pipe 14. The starting end of the bypass pipe 14 is connected to the first feed pipe 11, and the ending end is connected to the second feed pipe 12, located between the expander 42 and the feed position P32. This allows the bypass stream a14 of the first portion a1 of the feed air a0 to be sent to the second feed pipe 12, so that the bypass stream a14, together with the second portion a2, is fed into the feed position P32 of the mixing tower 23 as the feed gas for the mixing tower 23. The mixing tower 23 has a tray between the feed position P32 and the oxygen supply position P31 along its height.

[0039] The piping system 1 also includes a first output line 17. The first output line 17 is configured to output a low-purity oxygen stream so from the top of the mixing tower 23, which ultimately becomes the low-purity oxygen product Po.

[0040] Compared to Figure 2 In contrast, in the aforementioned low-purity oxygen production equipment 10, the second part a2 of the feed air a0 after being expanded by the expander 42 is sent into the mixing tower 23 through the second feed pipeline 12. This can result in a lower pressure in the feed stream of the mixing tower 23. Therefore, the pressure of the produced low-purity oxygen product Po is lower, which can better meet the low-pressure requirements and save energy consumption for further pressure reduction.

[0041] Moreover, compared to Figure 2 In contrast, in the aforementioned low-purity oxygen production equipment 10, the low-pressure tower 22 no longer receives the second portion a2 expanded by the expander 42, or at least no longer receives the entire second portion a2. Therefore, the flow rate of the second portion a2 expanded by the expander 42 is not easily limited due to restrictions on the intake volume of the low-pressure tower 22. Consequently, the expansion cooling capacity is not easily limited, thus providing flexibility for increasing the yield of liquid products.

[0042] Furthermore, by setting up a bypass line 14, a portion of the feed stream destined for distillation in the high-pressure tower 21 is utilized—specifically, the bypass stream a14 of the first portion a1 of the feed air a0—is fed into the mixing tower 23 together with the second portion a2 of the expanded feed air a0, serving as the upward flow of the mixing tower 23. This increases the yield of the low-purity oxygen product Po, meaning a higher yield of Po can be achieved, especially compared to the other proportion where the mixing tower 23 only receives a portion of the expanded feed air a0 as the feed stream. As mentioned later, a throttling valve is installed on the bypass line 14, thus providing design flexibility for yield adjustment.

[0043] It is understood that the terms "first" and "second" are used for descriptive purposes only and do not refer to limitations on chronological order, quantity, or importance. They should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated, but are merely used to distinguish one technical feature from another in this technical solution. Therefore, a feature specified with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "multiple" means two or more (i.e., more than two), unless otherwise explicitly specified. Similarly, qualifiers such as "one" appearing in the text do not refer to limitations on quantity, but rather describe technical features not previously mentioned. Likewise, unless a noun is modified by a specific quantifier, the text should be considered to include both singular and plural forms; the technical solution may include either a singular or plural number of that technical feature. Similarly, modifiers such as "approximately" or "about" preceding numerals in the text usually include the number itself, and their specific meaning should be understood in conjunction with the context. In addition, unless otherwise stated, descriptions such as "above", "below", "at least", and "at most" include the corresponding numerical value, while descriptions such as "higher than", "lower than", "more than", and "less than" do not include the corresponding numerical value.

[0044] It is also understood that when the text describes a stream entering the first and second elements sequentially, or uses similar descriptions, it only indicates the order in which the stream enters the first and second elements. It does not preclude the possibility that the stream passes through a third element between the first and second elements, or that the stream passes through a third element before or after the first element. For example, after the feed air a0 is pressurized by the main air compressor 3, it typically undergoes purification by a front-end purification device before being split into the first portion a1 and the second portion a2. However, the present invention can be limited to embodiments that only pass through all or part of the illustrated substantial elements, as needed. Substantive elements include, for example, the illustrated booster 41, expander 42, distillation column system 2, main heat exchanger 6, etc., and generally do not include piping elements such as valves or flow meters. In other words, in embodiments, for example, limited to those only passing through the illustrated substantial elements, such piping elements can be provided as needed.

[0045] Figure 1In the process, the feed air a0 is pressurized to a first pressure p1 by the main air compressor 3, and the first portion a1 is sent into the high-pressure tower 21 at the first pressure p1. The second portion a2 is expanded to a second pressure p2 by the expander 42, and the second portion a2 is sent into the mixing tower 23 at the second pressure p2, wherein the second pressure p2 is lower than the first pressure p1. A pressure reducing element 5 is installed in the bypass pipeline 14, and the bypass stream a14 is reduced to the second pressure p2 by the pressure reducing element 5 and then sent to the second feed pipeline 12. In this way, the pressure of the mixing tower 23 can be matched with the required pressure of the low-purity oxygen product Po, eliminating the limitation caused by the outlet pressure of the main air compressor 3.

[0046] like Figure 1 As shown, the pressure reducing element 5 can be a throttle valve configured to adjust the flow rate. By installing this pressure reducing element 5, a throttle valve, in the bypass line 14, pressure matching is not only easier to achieve, but the bypass flow rate can also be adjusted, thus allowing for flexible adjustment of the production of the low-purity oxygen product Po.

[0047] When describing pressure, natural pressure loss is generally not considered. If the pressure difference between corresponding parts is not greater than the natural line loss caused by pressure losses in pipes, heat exchangers, coolers, adsorbers, ordinary regulating valves (non-throttle valves), etc., even if this natural line loss is significant, the pressure is still rated as "equal". For example, after feed air a0 is pressurized to a first pressure p1 by the main air compressor 3, it actually passes through the main heat exchanger 6, etc., before reaching the high-pressure tower 21, resulting in some pressure loss, but the text still describes it as "the first part a1 is sent into the high-pressure tower 21 at the first pressure p1". Conversely, only when the corresponding pressure difference is higher than the natural line loss, that is, especially when the pressure is increased by at least one compressor stage or intentionally reduced by at least one throttle valve and / or at least one pressure reducing device (e.g., expander), will the pressure of the stream downstream of certain process steps be described as "lower" or "higher" than the pressure upstream of these process steps. The same applies to the description of temperature. Furthermore, in this case, the corresponding pressure and temperature can be in non-intersecting ranges or in overlapping ranges. Specifically, pressure includes, for example, unavoidable or anticipated pressure drops, and temperature includes, for example, unavoidable or anticipated temperature drops.

[0048] Figure 1 In the second feed line 12, a booster 41 and an aftercooler 44 can also be installed. The second feed line 12 is configured to sequentially pressurize the second part a2 of the feed air a0 through the booster 41, cool it through the aftercooler 44, and expand it through the expander 42 before sending it into the mixing tower 23. The above configuration can further improve the expansion refrigeration efficiency and the distillation efficiency. Figure 1In this configuration, expander 42 drives turbocharger 41. This includes two scenarios: the expansion work performed by expander 42 is at least partially provided to turbocharger 41, and the energy required for turbocharger 41 to boost pressure is at least partially derived from expander 42. Specifically, expander 42 and turbocharger 41 are the expansion end and boosting end of the same turboexpander, respectively; that is, all the expansion work performed by expander 42 is provided to turbocharger 41, and all the energy required for turbocharger 41 to boost pressure also originates from expander 42.

[0049] Figure 1 In the low-purity oxygen production equipment 10, a main heat exchanger 6 is also included. The piping system 1 is configured such that the feed air a0, after being pressurized by the main air compressor 3, is split into a first portion a1 and a second portion a2. The first portion a1, after being completely cooled by the main heat exchanger 6 via the first feed pipe 11, enters the high-pressure tower 21. The second portion a2, after being pressurized by the booster 41 and cooled by the aftercooler 44 via the second feed pipe 12, enters the main heat exchanger 6 for complete cooling, then expands via the expander 42, and finally enters the mixing tower 23. The low-purity oxygen stream so exiting from the top of the mixing tower 23 is completely reheated via the main heat exchanger 6 through the first output pipe 17, thus becoming the low-purity oxygen product Po.

[0050] It is understandable that the description here, "the feed air a0 is pressurized by the main air compressor 3 and then split into the first part a1 and the second part a2," does not preclude the possibility that the feed air a0 may also split into a third part. However, it can also be limited to splitting into only the first part a1 and the second part a2, without a third part. It is also understandable that "complete cooling" means that the cooled stream is sent to the main heat exchanger 6 at the hot end and then cooled to the cold end temperature of the main heat exchanger 6. "Partial cooling" means cooling to the temperature between the hot and cold ends of the main heat exchanger 6, referred to as "intermediate temperature." The same logic applies to expressions such as "complete reheating" and "partial reheating."

[0051] It can also be understood that the terms "pipeline," "pipeline," and "pipe segment" used in the text all refer to the route through which the flow stream passes, without limiting the physical form of the corresponding components. Taking "pipeline" as an example, a pipeline can refer to a segment of a complete pipeline. A pipeline can also be a combination of multiple pipelines connected sequentially. These multiple pipelines can be connected by pipe fittings or other pipeline components such as valves. The space through which the flow stream passes in the pipe fittings or other pipeline components can also be considered part of the pipeline.

[0052] The liquid oxygen lo exiting the evaporation space of the main condenser-evaporator 24 at position P41 can be higher than the oxygen delivery position P31, allowing the liquid oxygen lo to directly reach the oxygen delivery position P31 via head difference. "Directly reaching via head difference" means that the liquid oxygen lo directly reaches the mixing tower 23 from the main condenser-evaporator 24 via head difference, without the need for additional equipment. Figure 2 The booster pump 8 in the comparative example is used for pumping.

[0053] Figure 1 In this system, piping system 1 is also configured to allow the bottom liquid q3 accumulated at the bottom of mixing column 23 to be fed into low-pressure column 22. Piping system 1 is also configured to allow the intermediate stream s35 drawn from the middle position P35 of mixing column 23 to be fed into low-pressure column 22. This facilitates distillation.

[0054] The bottom liquid q3 is fed into the first intermediate position P24 of low-pressure column 22. The intermediate stream s35 is fed into the second intermediate position P25 of low-pressure column 22. The first intermediate position P24 is higher than the second intermediate position P25. This is beneficial for distillation.

[0055] Figure 1 In the process, the second portion a2, which has been expanded by expander 42, is entirely fed into mixing column 23. That is, low-pressure column 22 no longer receives the second portion a2, which further improves distillation efficiency.

[0056] Figure 1 In the mixing tower 23, oxygen feed point P31 is the high position above all trays, while feed point P32 is the low position below all trays. Part a1 is fed into the high-pressure tower 21 at the low position P12 below all trays.

[0057] It's understandable that when describing a distillation column, using "bottom" and "top" refers to the bottom and top positions of the column, respectively, typically facilitating the extraction of liquids and gases. Using "low position" and "high position" means all trays of the column are located above and below that position, respectively, while "middle position" means there are trays both above and below that position, i.e., at least one tray. Describing a position as "equivalent" means the number of trays above (or below) the point where the stream enters or exits is the same.

[0058] The following is combined Figure 1An exemplary embodiment is described. For example, the user requires a low-purity oxygen product Po of approximately 1.5 bara. The operating pressure of the high-pressure tower 21 is approximately 5.5 bara, and the operating pressure of the low-pressure tower 22 is approximately 1.3 bara. The first portion a1 of the feed air a0, pressurized by the main air compressor 3, enters the main heat exchanger 6 at 5.8 bara. The second portion a2 is pressurized to approximately 9 bara by the booster 41 and then introduced into the main heat exchanger 6. Afterward, it expands to 1.8 bara in the expander 42 and is then introduced into the mixing tower 23. The bypass stream a14 of the 5.8 bara first portion a1 is throttled to 1.8 bara and mixed with the expanded second portion a2, entering the mixing tower 23. Liquid oxygen lo with approximately 98% oxygen purity from the main condenser-evaporator 24 enters the mixing tower 23 as reflux liquid. The low-purity oxygen stream so, with approximately 95% oxygen purity, generated from mixing tower 23, is reheated to ambient temperature by main heat exchanger 6 and exits main heat exchanger 6 at approximately 1.5 bara.

[0059] Figure 1 The diagram also shows a pure nitrogen tower 25 located at the top of the low-pressure tower 22 (upper tower). Oxygen-enriched liquid q1 exiting from the bottom of the high-pressure tower 21 (lower tower) is cooled by subcooler 7 and enters the intermediate position P27 of the low-pressure tower 22. Oxygen-enriched stream s11 exiting from the lower intermediate position of the high-pressure tower 21 is subcooled by subcooler 7 and enters the intermediate position P26 of the low-pressure tower 22. Nitrogen-enriched liquid ln, condensed by heat exchange in the main condenser-evaporator 24, is subcooled by subcooler 7; a portion is exported as liquid nitrogen product Nl, and the other portion is introduced into the pure nitrogen tower 25. The stream exiting from the top of the low-pressure tower 22 is reheated sequentially by subcooler 7 and main heat exchanger 6, becoming waste nitrogen gas Wn. The stream exiting from the top of the pure nitrogen tower 25 is reheated sequentially by subcooler 7 and main heat exchanger 6, becoming nitrogen product Pn.

[0060] It is understood that when the text mentions that piping system 1 is configured to allow the corresponding flow streams to move in a certain way, it means that piping system 1 includes the corresponding pipelines, which are shown in the diagrams as lines with arrows indicating the direction of the flow streams. To avoid making the description too lengthy, not every line is represented by a corresponding pipeline, but the arrowed lines in the diagrams can be considered as one or more pipe segments, or one or more pipelines, as needed. Furthermore, it is understood that when the text uses terms such as "between," "after," "before," "upstream," "downstream," and similar expressions to describe the arrangement of the flow path, it is with reference to the corresponding flow stream direction.

[0061] Overall, the aforementioned low-purity oxygen production equipment utilizes a second portion of the expanded feed air entering the mixing tower, overcoming the limitations of comparative methods and enabling more efficient production of low-pressure, low-purity oxygen products. Specifically, by using a portion of the expanded feed air as the feed stream to the mixing tower, the operating pressure of the mixing tower can be directly matched to the required pressure of the low-purity oxygen product, thus enabling the low-pressure, low-purity oxygen product to be produced with low energy consumption.

[0062] Furthermore, the aforementioned low-purity oxygen production equipment also expands the equipment's versatility in producing high-purity nitrogen and liquid products. Specifically, the low-purity oxygen production equipment reduces the gas flow rate entering the upper column, which serves as a low-pressure tower. This significantly improves the oxygen recovery rate, potentially reaching up to 99%, while simultaneously enhancing the overall equipment's ability to produce liquid products.

[0063] Unless otherwise clearly indicated, each aspect or embodiment defined herein may be combined with any other aspect or embodiment. In particular, any feature indicated as preferred or advantageous may be combined with any other feature indicated as preferred or advantageous.

[0064] The embodiments described in this specification are merely preferred embodiments of the present invention. These embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of the present invention. All technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation should be within the scope of the present invention.

Claims

1. A low-purity oxygen production device, which obtains low-purity oxygen product through air separation, the low-purity oxygen production device comprising a piping system and a distillation column system, the distillation column system comprising a high-pressure column, a low-pressure column and a mixing column, the high-pressure column and the low-pressure column being thermally connected via a main condenser-evaporator, the piping system comprising a first feed pipeline and an oxygen supply pipeline, the first feed pipeline being configured to send a first portion of the feed air pressurized by the main air compressor into the high-pressure column for distillation, the oxygen supply pipeline being configured to send liquid oxygen from the evaporation space of the main condenser-evaporator into the oxygen supply position of the mixing column as reflux liquid of the mixing column; Its features are, The piping system also includes: The second feed line is equipped with an expander and is configured to expand a second portion of the feed air that has been pressurized by the main air compressor and then send it into the feed position of the mixing tower. A bypass line is provided, the starting end of which is connected to the first feed line, and the ending end of which is connected to the second feed line between the expander and the feed position. This bypass flow of the first portion of the feed air is then delivered to the second feed line, so that the bypass flow, together with the second portion, is fed into the feed position of the mixing tower as feed gas. The mixing tower has a tray positioned between the feed position and the oxygen delivery position along its height. The first output pipeline is configured to output a stream of low-purity oxygen from the top of the mixing tower, which ultimately becomes the low-purity oxygen product.

2. The low-purity oxygen production equipment as described in claim 1, characterized in that, The feed air is pressurized to a first pressure by the main air compressor, and the first portion is sent into the high-pressure tower under the first pressure; The second portion expands to a second pressure via the expander, and the second portion is fed into the mixing tower at the second pressure, wherein the second pressure is less than the first pressure; The bypass pipeline is equipped with a pressure reducing element, and the bypass stream is sent to the second feed pipeline after being reduced to the second pressure by the pressure reducing element.

3. The low-purity oxygen production equipment as described in claim 2, characterized in that, The pressure reducing element is a throttle valve configured to adjust the flow rate.

4. The low-purity oxygen production equipment as described in claim 1, characterized in that, The second feed line is also equipped with a booster and an aftercooler. The second feed line is configured to sequentially pressurize the second part of the feed air through the booster, cool it through the aftercooler, expand it through the expander, and then send it into the mixing tower. The expander drives the booster.

5. The low-purity oxygen production equipment as described in claim 4, characterized in that, It also includes the main heat exchanger; The piping system is configured such that the feed air, after being pressurized by the main air compressor, is split into the first part and the second part; The first portion, after being completely cooled by the main heat exchanger through the first feed pipeline, enters the high-pressure tower; The second part first enters the booster for pressurization through the second feed pipeline and is cooled by the aftercooler, then enters the main heat exchanger for complete cooling, and then expands through the expander before finally entering the mixing tower; The low-purity oxygen stream exiting from the top of the mixing tower is fully reheated via the main heat exchanger through the first output pipeline, thereby becoming the low-purity oxygen product.

6. The low-purity oxygen production equipment as described in claim 1, characterized in that, The liquid oxygen exits from the evaporation space of the main condenser at a position higher than the oxygen delivery point, allowing the liquid oxygen to directly reach the oxygen delivery point through the head difference.

7. The low-purity oxygen production equipment as described in claim 1, characterized in that, The piping system is also configured to allow the bottom liquid accumulated at the bottom of the mixing tower to be fed into the low-pressure tower; The piping system is also configured such that an intermediate stream drawn from the middle of the mixing tower is fed into the low-pressure tower.

8. The low-purity oxygen production equipment as described in claim 7, characterized in that, The bottom liquid is fed into the first intermediate position of the low-pressure tower, and the intermediate stream is fed into the second intermediate position of the low-pressure tower. The first intermediate position is higher than the second intermediate position.

9. The low-purity oxygen production equipment as described in claim 1, characterized in that, The second portion, after being expanded by the expander, is entirely fed into the mixing tower.

10. The low-purity oxygen production equipment as described in claim 1, characterized in that, The oxygen delivery position is the high position of the mixing tower located above all the trays, while the feed position is the low position of the mixing tower located below all the trays. The first portion is fed into the low position below all the tower plates of the high-pressure tower.

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