Cooling water supply system and air separation plant

Abstract

The utility model provides a kind of cooling water supply system and air separation equipment.In cooling water supply system, first water supply pipeline is set to supply first part cooling water to the cooling water inlet of refrigerator of precooling system.In which, the chilled water produced by refrigerator enters the air pre-cooler of precooling system to supply cooling for the feed air of air separation equipment, so as to form recovery water by temperature rising.Bypass pipeline is set to make at least part of recovery water from air pre-cooler flow into first water supply pipeline.The above-mentioned cooling water supply system can guarantee that the water temperature of refrigerator at cooling water inlet in precooling system of air separation equipment meets lower limit requirement.

Description

Technical Field

[0001] This utility model belongs to the field of air separation and relates to an air separation device. In particular, it relates to a cooling water supply system that can supply cooling water to the precooling system of the air separation device. Background Technology

[0002] In air separation units, the precooling system, used to precool the feed air, typically employs a chiller to provide chilled water, thus precooling the feed air. Before reaching the precooling system, the feed air is usually compressed by an air compressor, often referred to as the main air compressor. These chillers themselves also require cooling water to cool the incoming water to the required temperature for precooling. The water supply unit, for example, is a cooling tower, which circulates cooling water through the chiller's condenser to remove heat.

[0003] In practice, it has been found that chillers have a lower limit requirement for the water temperature at their cooling water inlet. In cold weather conditions such as winter, this water temperature may drop below the required lower limit. This can cause unstable operation of the chiller, or even shutdown.

[0004] Therefore, there is a need to provide a cooling water supply system that can cope with the above operating conditions. Utility Model Content

[0005] The purpose of this invention is to provide a cooling water supply system that can ensure that the water temperature at the cooling water inlet of the chiller in the precooling system of the air separation unit meets the lower limit requirement.

[0006] This invention provides a cooling water supply system. The cooling water supply system is configured to supply cooling water to the precooling system of an air separation unit. The cooling water supply system includes a first water supply pipeline. The first water supply pipeline is configured to supply a first portion of cooling water to the cooling water inlet of the chiller in the precooling system. The chilled water produced by the chiller enters the air precooler of the precooling system to cool the feed air of the air separation unit, thereby raising its temperature and forming recycled water. The cooling water supply system also includes a bypass pipeline. The bypass pipeline is configured to allow at least a portion of the recycled water from the air precooler to flow into the first water supply pipeline.

[0007] In one implementation, the air precooler is an air-cooled tower.

[0008] In one embodiment, the cooling water supply system further includes a second water supply line. The second water supply line is configured to supply a second portion of cooling water to the air-cooled tower of the precooling system. The recycled water is formed by the second portion of cooling water and chilled water being heated through heat exchange with the feed air of the air separation unit.

[0009] In one embodiment, the cooling water supply system further includes a first return water line. The first return water line is configured to return a portion of the cooling water that has heated up after being cooled in the chiller to the supply water unit. The supply water unit supplies cooling water to the pre-cooling system. The cooling water supply system also includes a second return water line extending from the bottom of the air-cooled tower to the supply water unit. A bypass line is connected at its starting end to the second return water line and at its ending end to the first supply water line. The supply water unit is a cooling tower.

[0010] In one implementation, the air precooler is a shell-and-tube heat exchanger.

[0011] In one embodiment, the cooling water supply system further includes a switching valve. The switching valve is located on a bypass line to regulate the opening and closing of the bypass line.

[0012] In one embodiment, the switching valve is a regulating valve configured to adjust the flow rate in a bypass line.

[0013] In one embodiment, the cooling water supply system further includes a temperature detector and a controller. The temperature detector is configured to detect the water temperature at the cooling water inlet of the chiller. The controller is configured to send an opening / closing signal to the switching valve based on the temperature signal indicating the water temperature transmitted by the temperature detector. The controller is also configured to send an adjustment signal to the switching valve based on the temperature signal to adjust the opening degree of the switching valve.

[0014] In one embodiment, the cooling water supply system further includes a third water supply line. The third water supply line is configured to supply a third portion of the cooling water to the nitrogen tower of the precooling system. After being cooled by heat exchange with the waste nitrogen from the air separation unit in the nitrogen tower, the third portion of the cooling water enters the chiller as chilled water.

[0015] This invention also provides an air separation unit. The air separation unit includes a precooling system. The precooling system includes an air precooler and a refrigeration unit. The refrigeration unit is configured to supply chilled water to the air precooler, thereby precooling the feed air. The air separation unit also includes the aforementioned cooling water supply system.

[0016] When using the aforementioned cooling water supply system and air separation equipment, for example, when the ambient temperature is too low, at least a portion of the higher-temperature recycled water (formed by the chilled water entering the air precooler for cooling) can be mixed with the lower-temperature first portion of cooling water supplied directly through the water supply unit via a bypass pipeline. This increases the temperature of the cooling water used in the chiller. Therefore, it effectively ensures that the water temperature at the cooling water inlet of the chiller in the precooling system of the air separation equipment meets the lower limit requirement and is not too low, making it particularly suitable for cold weather.

[0017] The above structure utilizes the heat obtained by the chilled water produced by the chiller after cooling, without the need for additional heat sources. It is simple in structure and low in cost. Attached Figure Description

[0018] The advantages and spirit of this utility model can be further understood through the following detailed description and accompanying drawings.

[0019] Figure 1 This is a schematic diagram of an exemplary cooling water supply system according to the first embodiment.

[0020] Figure 2 This is a schematic diagram of an exemplary cooling water supply system according to the second embodiment. Detailed Implementation

[0021] 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.

[0022] 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.

[0023] 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.

[0024] As mentioned earlier, the pre-cooling of air in the air separation unit by the refrigeration unit is crucial; its shutdown can lead to reduced load or even complete shutdown of the entire air separation unit. Furthermore, the temperature of the cooling water entering the refrigeration unit's condenser at the refrigeration unit's cooling water inlet must not be too low, otherwise, malfunctions or even damage may occur. Therefore, effectively ensuring this is extremely important.

[0025] In particular, it is necessary to consider how to design the cooling water supply system to supply cooling water to the chiller, so as to avoid abnormal situations caused by excessively low cooling water temperature, such as in winter. Furthermore, how to make full use of existing facilities to achieve a simple and low-cost construction is also an issue that needs to be considered.

[0026] Figure 1 A cooling water supply system 2 according to a first embodiment is illustrated. The cooling water supply system 2 is configured to supply cooling water w0 to the precooling system 1 of the air separation unit 10. 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 the present invention.

[0027] It is understandable that the air precooler 4, the refrigeration unit 8, and the nitrogen tower 7 mentioned later can together constitute the precooling system 1 of the air separation unit 10.

[0028] The cooling water supply system 2 includes a first water supply line 21. The first water supply line 21 is configured to supply a first portion of cooling water w1 to the cooling water inlet P1 of the chiller 8 in the precooling system 1. The chilled water q1 produced by the chiller 8 enters the air precooler 4 of the precooling system 1 to cool the feed air a0 of the air separation unit 10, thereby raising its temperature to form recycled water q4.

[0029] A chiller, or chilled water machine, requires cooling water to pass through its condenser for cooling, thus enabling it to produce chilled water. It's important to understand that the chilled water produced by a chiller is not formed from the cooling water entering the condenser's inlet, but rather from a separate inlet, which will be explained in detail later.

[0030] Figure 1 In this system, the cooling water supply system 2 also includes a bypass pipe 28. The bypass pipe 28 is configured to allow at least a portion q41 of the recycled water q4 from the air precooler 4 to flow into the first water supply pipe 21. That is, after the recycled water q41 is combined with the first portion of cooling water w1, it is sent together to the cooling water inlet P1 of the chiller 8 as the chiller cooling water c1.

[0031] It is understandable that the chiller cooling water c1 entering the cooling water inlet P1 and the chilled water q1 entering the chiller inlet P3 and exiting the chiller outlet P4 are not the same stream; they are completely independent. Figure 1 The interior of the intermediate chiller 8 is schematically shown with two independent pipelines.

[0032] In the aforementioned cooling water supply system 2, by setting up a bypass pipe 28, at least a portion q41 of the heated recycled water q4 from the air precooler 4 is combined with the first portion of cooling water w1, which has a lower temperature, originating from the water supply unit 3. This increases the water temperature T1 of the chiller cooling water c1 at the cooling water inlet P1 of the chiller 8. Therefore, the problem of unstable operation or shutdown of the chiller 8 in cold weather due to the low temperature of the cooling water w0 supplied by the water supply unit 3 can be solved.

[0033] The cooling water supply system 2 mentioned above makes full use of existing water sources, has a simple structure, low cost, and stable hydraulics, which can ensure that the chiller 8 can operate stably under cold conditions.

[0034] It is understood that the terms "pipeline," "pipeline," and "pipe segment" used in the text all refer to the route through which the flow stream passes, and do not limit 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 by 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.

[0035] It can also be understood that when the text describes a stream entering the first element and the second element in sequence, or uses similar descriptions, it only indicates the order in which the stream enters the first element and the second element. It does not exclude the possibility that the stream passes through the second element between the first element and the second element, nor does it exclude the possibility that the stream passes through the second element before the first element or after the second element.

[0036] Figure 1 In the cooling water supply system 2, a switching valve 5 may also be included. The switching valve 5 is located on the bypass line 28 to regulate its opening and closing. This allows the bypass line 28 to be opened when the ambient temperature is low, such as in winter, allowing at least a portion of the recycled water q41 to be mixed with the first portion of cooling water w1, thus raising the temperature of the resulting chiller cooling water c1 entering the cooling water inlet P1. When the ambient temperature is not too low, such as in summer, the normally closed switching valve 5 shuts off the bypass line 28, using only the first portion of cooling water w1 as the chiller cooling water c1. Specifically, the switching valve 5 can be a regulating valve configured to adjust the flow rate in the bypass line 28. Therefore, the mixing ratio can be adjusted, and the temperature after mixing can be regulated. As mentioned earlier, the feed air a0 is typically pressurized before reaching the air precooler 4, and the switching valve 5 can also act as a throttling valve to reduce pressure.

[0037] See also Figure 1The cooling water supply system 2 may also include a temperature detector 61 and a controller 62. The temperature detector 61 is configured to detect the water temperature T1 at the cooling water inlet P1 of the chiller 8. The controller 62 may be configured to send a switching signal S5 to the switching valve 5 to open / close it based on the temperature signal S1 indicating the water temperature T1 transmitted by the temperature detector 61. The controller 62 sends the switching signal S5 to the switching valve 5 to achieve mode switching, thereby responding to different conditions, such as suitable or excessively low external environmental temperatures. This allows for automatic control.

[0038] As mentioned earlier, the switching valve 5 can be a regulating valve with adjustable flow rate. In this case, the controller 62 can also be configured to send a regulating signal S6 to the switching valve 5 to adjust its opening degree based on the temperature signal S1. Thus, precise temperature control of the water temperature T1 at the cooling water inlet P1 can be achieved by controlling the flow rate of the bypass pipe 28.

[0039] The controller 62 may be one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DAPDs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, or combinations thereof. The temperature detector 61 may be, for example, various sensors, such as contact sensors like thermocouples, or non-contact sensors like infrared sensors. Figure 1 The signal connections between the controller 62 and the temperature detector 61, and the switching valve 5, etc., are schematically shown in dashed lines. It can be understood that the signal connections can be wired or wireless.

[0040] Figure 1 In this diagram, the air precooler 4 is an air-cooled tower 41. The air-cooled tower 41 is also commonly referred to as a water-washing tower. In the air-cooled tower 41, the feed air a0 generally comes into direct contact with the chilled water q1 produced by the chiller 8 and is thus precooled. Typically, the chilled water q1 enters the air-cooled tower 41 at a higher position H1, while a second portion of cooling water w2 enters the air-cooled tower 41 at a middle position H2 to achieve a reasonable temperature gradient layout, which will be described shortly. The diagram shows the feed air a0 entering the air-cooled tower 41 from a lower position and exiting from the top after cooling, indicated by a dashed line with an arrow.

[0041] Figure 1In this system, the cooling water supply system 2 may further include a second water supply line 22. The second water supply line 22 is configured to supply a second portion of cooling water w2 to the air-cooled tower 41 of the precooling system 1. The recycled water q4 is formed by the second portion of cooling water w2 and chilled water q1 being heated together through heat exchange with the feed air a0 of the air separation unit 10. That is, the recycled water q4 includes the relatively warm water accumulated at the bottom of the tower due to direct heat exchange between the second portion of cooling water w2 and the feed air a0, and also includes the relatively warm water accumulated at the bottom of the tower due to direct heat exchange between the chilled water q1 and the feed air a0.

[0042] 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 this text, "multiple" means two or more (i.e., more than two), unless otherwise explicitly specified. Similarly, qualifiers like "one" appearing in this 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, it should be considered to include both singular and plural forms in this text; the technical solution may include either a singular or plural number of that technical feature.

[0043] Figure 1 In this system, the cooling water supply system 2 may further include a first return water line 25. The first return water line 25 is configured to return the first portion of cooling water w1 that has heated up after being cooled in the chiller 8 to the water supply unit 3. The water supply unit 3 supplies the aforementioned cooling water w0 to the precooling system 1. That is, the water supply unit 3 is the cooling water source that supplies the aforementioned cooling water w0 to the precooling system 1. In the case of mixing at least a portion q41 of the recycled water q4, the first return water line 25 will return the first portion of cooling water w1 mixed with at least a portion q41 to the water supply unit 3.

[0044] Figure 1 It is also shown that the cooling water supply system 2 may further include a second return water pipe 26 leading from the bottom of the air-cooled tower 41 to the water supply unit 3. The starting end of the bypass pipe 28 is connected to the second return water pipe 26, while the ending end is connected to the first water supply pipe 21. That is, a portion of the recycled water q4 from the bottom of the air-cooled tower 41 flows into the first water supply pipe 21, while the other portion q42 is recycled back to the water supply unit 3.

[0045] Specifically, water supply unit 3 can be a cooling tower. A cooling tower typically consists of a tower body and a water tank. The tower body usually contains a fan to cool the feed water entering from the middle or upper part of the tower to a lower temperature, after which it is discharged downwards under gravity. The water tank is placed at the bottom of the tower body to collect the cooler drainage flowing down from the tower, thus allowing the output of cooling water w0. The recycling mentioned in the text can all be directed to the cooling tower body, while the water supply can be drawn from the water tank.

[0046] Figure 1 In the cooling water supply system 2, a third water supply line 23 is also included. The third water supply line 23 is configured to supply a third portion of cooling water w3 to the nitrogen tower 7 of the precooling system 1. After being cooled by heat exchange with the waste nitrogen wn from the air separation unit 10 in the nitrogen tower 7, the third portion of cooling water w3 enters the chiller 8 to become chilled water q1. It can be understood that the description of the heat exchange between the third portion of cooling water w3 and the waste nitrogen wn also includes the case where the third portion of cooling water w3 exchanges heat with a low-temperature gas flow, a portion of which is waste nitrogen wn. That is, the low-temperature gas flow is a mixture of waste nitrogen wn and other gases, such as low-pressure nitrogen products. The figure shows, with a dashed line bearing an arrow, waste nitrogen wn entering the nitrogen tower 7 from a lower position and exiting from the top after reheating. The figure also shows the inlet water q7 exiting the nitrogen tower 7 and about to enter the chiller 8 to be cooled and become chilled water q1.

[0047] Figure 2 An exemplary cooling water supply system 2 according to a second embodiment is shown. Figure 2 The similar labels in the text indicate the similarity to Figure 1 Elements similar to those in the first embodiment are omitted from repeated description. Figure 1 The main difference is that, Figure 2 In this configuration, the air precooler 4 is a shell-and-tube heat exchanger 42. Feed air a0 and chilled water q1 exchange heat indirectly within the shell-and-tube heat exchanger 42. The shell-and-tube heat exchanger 42 does not receive cooling water from the water supply unit 3, meaning it does not receive cooling water from the water supply unit 3. Figure 1 The second water supply pipeline 22 in the middle.

[0048] like Figure 1 As shown, this utility model also provides an air separation unit 10. The air separation unit 10 includes a precooling system 1. The precooling system 1 includes an air precooler 4 and a chiller 8. The chiller 8 is configured to supply chilled water q1 to the air precooler 4, thereby precooling the feed air a0. The air separation unit 10 may also include the aforementioned cooling water supply system 2.

[0049] By employing the aforementioned cooling water supply system, the inlet temperature of the chiller cooling water can be effectively increased in cold weather, maintaining it above the required minimum limit. This ensures the stable operation of the chiller and the entire air separation unit, preventing abnormal operating conditions such as load reduction or shutdown. Furthermore, this solution is cost-effective, simple in construction, and energy-efficient. Moreover, the use of adjustable flow switching valves and temperature feedback-based controllers allows for precise proportional mixing of the higher-temperature recovery water in the bypass line and the lower-temperature cooling water in the primary supply line. Therefore, the inlet temperature of the chiller cooling water can be accurately and stably controlled at the target setpoint. Additionally, this arrangement minimizes hydraulic disturbance to the main cooling water network, resulting in more stable operation.

[0050] 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.

[0051] 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 cooling water supply system configured to supply cooling water to a precooling system of an air separation unit, the cooling water supply system comprising a first water supply pipeline configured to supply a first portion of cooling water to the cooling water inlet of the chiller of the precooling system, wherein, The chilled water produced by the chiller enters the air precooler of the precooling system to cool the feed air of the air separation unit, thereby raising its temperature to form recycled water. The cooling water supply system is characterized in that it further includes a bypass pipeline, which is configured to allow at least a portion of the recycled water from the air precooler to flow into the first water supply pipeline.

2. The cooling water supply system as described in claim 1, characterized in that, The air precooler is an air-cooled tower.

3. The cooling water supply system as described in claim 2, characterized in that, It also includes a second water supply line, which is configured to supply a second portion of cooling water to the air-cooled tower of the precooling system. The recycled water is formed by the second portion of cooling water and the chilled water being heated together after heat exchange with the feed air of the air separation unit.

4. The cooling water supply system as described in claim 3, characterized in that, The cooling water supply system further includes a first return water pipeline, which is configured to return the first portion of cooling water that has been heated after being cooled in the chiller to the water supply unit, and the water supply unit supplies the cooling water to the precooling system. The cooling water supply system also includes a second return water pipeline from the bottom of the air-cooled tower to the water supply unit, wherein the starting end of the bypass pipeline is connected to the second return water pipeline, and the ending end is connected to the first water supply pipeline. The water supply unit is a cooling tower.

5. The cooling water supply system as described in claim 1, characterized in that, The air precooler is a shell-and-tube heat exchanger.

6. The cooling water supply system as described in claim 1, characterized in that, It also includes a switching valve, which is disposed on the bypass pipeline to regulate the opening and closing of the bypass pipeline.

7. The cooling water supply system as described in claim 6, characterized in that, The switching valve is a regulating valve configured to adjust the flow rate in the bypass pipeline.

8. The cooling water supply system as described in claim 7, characterized in that, It also includes a temperature detector and a controller; The temperature detector is configured to detect the water temperature at the cooling water inlet of the chiller; The controller is configured to send a switching signal to the switching valve to open or close the switching valve based on the temperature signal indicating the water temperature transmitted by the temperature detector; The controller is also configured to send an adjustment signal to the switching valve to adjust the opening degree of the switching valve based on the temperature signal.

9. The cooling water supply system as described in claim 1, characterized in that, It also includes a third water supply pipeline, which is configured to supply a third portion of cooling water to the nitrogen tower of the precooling system. The third portion of cooling water is cooled down by exchanging heat with the waste nitrogen of the air separation unit in the nitrogen tower and then enters the chiller to become the chilled water.

10. An air separation unit, comprising a precooling system, the precooling system including an air precooler and a chiller, the chiller being configured to supply chilled water to the air precooler to precool the feed air, characterized in that, The air separation unit further includes a cooling water supply system as described in any one of claims 1 to 9.

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