Air separation plant with aftercooler energy saving system

Abstract

The utility model discloses a kind of air separation equipment energy-saving systems with back cooler, belong to air separation technical field.The system is additionally provided with a back cooler on the pipeline between the air compressor outlet and molecular sieve purification system outlet.By the back cooler, high-temperature air output by air compressor and low-temperature air output by molecular sieve purification system carry out efficient countercurrent heat exchange.This move utilizes the cold energy of low-temperature air to precool high-temperature compressed air on the one hand, significantly reduces the refrigeration load of subsequent precooling unit, realizes energy saving;On the other hand, the temperature of air entering rectifying column is improved using the heat of high-temperature air, and the cold energy is recovered, avoiding energy waste.The utility model is especially suitable for air-cooled small-sized air separation device, by integrating back cooler and air-cooled system of air compressor, overall heat dissipation efficiency can be further improved, with the characteristics of compact structure, significant energy-saving effect, low modification cost and quick investment return.

Description

Technical Field

[0001] This utility model belongs to the field of energy-saving technology for air separation equipment, and specifically relates to an energy-saving system for air separation equipment with a return cooler. Background Technology

[0002] In traditional air separation processes, the high-temperature compressed air (typically between 10 and 55°C) output from the air compressor first enters the precooling unit, where it is forcibly cooled to 5 to 7°C, condensing most of the water. It then enters the molecular sieve purification system for the removal of moisture and carbon dioxide. This classic process has long suffered from two significant energy efficiency defects. First, the precooling unit consumes a large amount of electrical energy to counteract the sensible heat of the air, accounting for over 25% of the total energy consumption of the entire air separation unit, making it one of the major energy-consuming components. Second, the outlet air temperature after molecular sieve purification is typically low, often below 10°C. The valuable cold energy contained within is not effectively recovered in the current process but instead enters the cold box directly with the air. This not only wastes cold energy but can sometimes even increase the heat load on the main heat exchanger, creating an unreasonable offsetting effect of cold energy and further reducing the overall energy efficiency of the system.

[0003] To address the aforementioned energy efficiency issues, the industry has proposed several improvement technologies. For example, Chinese patent CN222393175U attempts to recover the cooling energy of the nitrogen gas from the product, but this solution does not address the core issue of recovering the cooling energy of the air exiting the molecular sieve. Another patent, CN222617370U, primarily reduces resistance by optimizing the pipeline structure, but its energy-saving effect is relatively limited. Especially for air-cooled small air separation units, which rely on air convection for heat dissipation and have inherently low heat dissipation efficiency, the refrigeration load on the pre-cooling unit is even heavier, making the energy efficiency contradiction particularly prominent. Therefore, existing technologies do not provide a targeted solution that can effectively recover the cooling energy of the air exiting the molecular sieve and significantly reduce the load on the pre-cooling unit. This has become a technical bottleneck for improving the economy and energy efficiency of such units, especially air-cooled small air separation units. Utility Model Content

[0004] This utility model aims to provide an energy-saving system for air separation equipment with a recirculating cooler, in order to solve the technical problem that the overall energy efficiency of the air separation process is low due to the failure to recover the cold air at the molecular sieve outlet and the excessive power consumption of the precooling unit.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: An energy-saving system for an air separation unit with a recirculating cooler includes an air compressor, a precooling unit, a molecular sieve purification system, and a distillation column; A cooler is installed between the outlet pipe of the air compressor and the outlet pipe of the molecular sieve purification system. The cooler includes a hot end and a cold end. The hot end inlet of the cooler is connected to the outlet of the air compressor, and the hot end outlet of the cooler is connected to the inlet of the precooling unit. The cold end inlet of the recooler is connected to the outlet of the molecular sieve purification system, and the cold end outlet of the recooler is connected to the inlet of the distillation column. By allowing the high-temperature air from the air compressor outlet and the low-temperature air from the molecular sieve purification system outlet to exchange heat in a countercurrent manner within the recooler, energy recovery and airflow temperature matching are achieved.

[0006] Furthermore, the air compressor is an air-cooled compressor unit.

[0007] Furthermore, the recooler is a plate-fin heat exchanger.

[0008] Compared with the prior art, the beneficial effects of this utility model are as follows: By setting a recooler between the air compressor and the precooling unit, this utility model cleverly recovers the cold energy of the low-temperature air at the molecular sieve outlet to precool the high-temperature air at the air compressor outlet. This not only significantly reduces the cooling load of the precooling unit (up to 45% in actual measurements) and achieves a substantial reduction in system energy consumption, but also avoids the waste of cold energy and potential equipment damage caused by the direct entry of low-temperature air into the cold box. In particular, for air-cooled air separation units, by integrating and optimizing the recooler with the air compressor's air-cooled radiator, the overall heat dissipation efficiency is improved, and the start-up and shutdown frequency of the precooling unit is reduced. At the same time, the system ensures operational flexibility through a bypass design, and the overall modification only requires the addition of one heat exchanger, which has the outstanding advantages of low cost and short investment payback period. Attached Figure Description

[0009] The accompanying drawings are provided to further illustrate the present invention and form part of the specification. They are used together with the embodiments of the present invention to explain the present invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the structure of an energy-saving system for an air separation unit with a recirculating cooler according to the present invention. Detailed Implementation

[0010] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0011] The present invention will be further described in detail below with reference to the embodiments. Example

[0012] like Figure 1 As shown, this embodiment provides an energy-saving system for an air separation unit with a recirculating cooler, including an air compressor 1, a precooling unit 2, a molecular sieve purification system 3, a distillation column 4, and a recirculating cooler 5 installed between the outlet pipe of the air compressor 1 and the outlet pipe of the molecular sieve purification system 3.

[0013] Air compressor 1 is used to compress air to the required pressure. Its discharge capacity is 200 Nm³ / min, and its outlet temperature is approximately 40°C. The high-temperature air from the outlet of air compressor 1 enters the cooler 5 and the precooling unit 2 sequentially through the main pipeline. In the cooler 5, it undergoes countercurrent heat exchange with the low-temperature air from the outlet of the molecular sieve purification system 3.

[0014] The recooler 5 adopts an aluminum plate-fin heat exchanger structure with a heat exchange area of ​​15㎡. Its hot end inlet is connected to the outlet of air compressor 1, and its hot end outlet is connected to the inlet of precooling unit 2; its cold end inlet is connected to the outlet of molecular sieve purification system 3, and its cold end outlet is connected to the inlet of distillation column 4.

[0015] During operation, the high-temperature air (approximately 40°C) output from air compressor 1 enters the hot end of cooler 5, where it undergoes countercurrent heat exchange with the low-temperature air (approximately 10°C) from the outlet of molecular sieve purification system 3. After heat exchange, the high-temperature air temperature drops to approximately 25°C and then enters precooling unit 2 for deep cooling; the low-temperature air temperature rises to approximately 20°C and then enters distillation column 4 for separation.

[0016] By installing the recirculating cooler 5, pre-cooling of the exhaust gas from the air compressor 1 is achieved, reducing the refrigeration load of the pre-cooling unit 2. Actual test results show that, compared to the traditional air separation process, the refrigeration load of the pre-cooling unit 2 in this embodiment is reduced by approximately 45%, and based on 8000 hours of annual operation, the energy savings can reach approximately 120,000 kWh. Example

[0017] Based on Example 1, this example integrates and optimizes the arrangement of the cooler 5 and the air-cooled air compressor 1.

[0018] Specifically, the air compressor 1 adopts an air-cooled compressor unit, and the heat dissipation fins of its air-cooled radiator extend and cover the high-temperature side surface of the return cooler 5, so that the two form an integrated heat dissipation module; the airflow of the air compressor 1's own fan is used to cool the shells of the air cooler and the return cooler 5 at the same time, thereby improving the overall heat dissipation efficiency of the system.

[0019] During operation, when the air compressor 1 fan starts, the airflow simultaneously acts on the heat exchange fins on the high-temperature side of the cooler 5, further reducing the outlet gas temperature of the cooler 5; during the molecular sieve regeneration stage, by setting a bypass valve group, the air flow path is switched to a direct flow mode to avoid energy consumption caused by ineffective heat exchange.

[0020] Actual measurements show that this integrated design reduces the start-up and shutdown frequency of the precooling unit 2 by about 60%, significantly extends the service life of the air compressor 1 and the precooling system, and reduces piping space and pressure loss.

[0021] As can be seen from the above embodiments, the energy-saving system of the air separation equipment with a recirculating cooler 5 of the present invention achieves the dual effects of compressed air waste heat recovery and low-temperature gas preheating by adding a recirculating heat exchange link between the air compressor 1 and the molecular sieve, effectively reducing the load of the precooling unit 2 and improving the overall energy efficiency of the system. It is particularly suitable for small and medium-sized air separation equipment and air-cooled air compressor 1.

[0022] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0023] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An energy-saving system for an air separation unit with a recirculating cooler, characterized in that: Includes air compressors, precooling units, molecular sieve purification systems, and distillation columns; A cooler is installed between the outlet pipe of the air compressor and the outlet pipe of the molecular sieve purification system. The cooler includes a hot end and a cold end. The hot end inlet of the cooler is connected to the outlet of the air compressor, and the hot end outlet of the cooler is connected to the inlet of the precooling unit. The cold end inlet of the recooler is connected to the outlet of the molecular sieve purification system, and the cold end outlet of the recooler is connected to the inlet of the distillation column. By allowing the high-temperature air from the air compressor outlet and the low-temperature air from the molecular sieve purification system outlet to exchange heat in a countercurrent manner within the recooler, energy recovery and airflow temperature matching are achieved.

2. The energy-saving system for an air separation unit with a return cooler according to claim 1, characterized in that: The air compressor is an air-cooled compressor unit.

3. The energy-saving system for an air separation unit with a recirculating cooler according to claim 2, characterized in that: The recooler is a plate-fin heat exchanger.

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