System and method for reducing energy consumption of multi-stage refrigerant compressor

Abstract

The invention discloses a system and a method for reducing the energy consumption of a multi-stage refrigerant compressor, and particularly relates to a four-stage two-stage refrigerant compressor applied to an LNG (Liquefied Natural Gas) device and the like. According to the system, in a first compression section of a multi-stage compressor at least comprising a first compression stage and a second compression stage, an interstage cooling device (such as a water cooler) is additionally arranged between an outlet of the first compression stage and an inlet of the second compression stage. And the high-temperature refrigerant is cooled from the first-stage outlet and then is fed into the second-stage compression, so that the power consumption of the subsequent compression stage is effectively reduced, and the total operation power and the energy consumption cost of the compressor are remarkably reduced. The method is simple, effective and remarkable in energy-saving effect. The invention also relates to a corresponding pipeline support design to ensure stable operation of the system.

Description

Technical Field

[0001] The present invention relates to a system and method for reducing the energy consumption of a multi-stage refrigerant compressor, belonging to the technical field of LNG. Background Art

[0002] In processes such as LNG liquefaction that require deep refrigeration, a multi-stage compressor is usually used to compress and circulate the refrigerant. For example, the refrigerant compressor in the Zunyi LNG storage and distribution project operates in a four-stage and two-section mode, where the outlet of the first stage is connected to the inlet of the second stage, and the outlet of the third stage is connected to the inlet of the fourth stage. Each section (including two stages) is provided with inlet and outlet pipelines, and the outlet pipeline usually passes through a cooler (such as an air cooler or a water cooler) to be cooled down and then reused or enter the next process.

[0003] Reference Figure 1 , in the original design, the total power of this type of compressor is a key operating cost factor. Taking the above project as an example, the total power of the originally designed four-stage and two-section compressor was contractually agreed to be 6700 KW, but it may reach about 6900 KW during simulated operation. Although this may be within the allowable deviation range of the contract (such as +4%), the relatively high actual operating power directly leads to significant energy consumption and high operating costs. Through specific analysis, it is found that in the original design, the temperature of the refrigerant after the first-stage compression is relatively high (about 97°C), and it directly enters the second-stage compression. This part of the heat increases the burden on the subsequent compression stages and is one of the reasons for the relatively high total power consumption. How to effectively reduce such multi-stage compressors, especially the inter-stage temperature, to achieve the purpose of energy conservation and consumption reduction is a technical problem faced by this field. Summary of the Invention

[0004] To solve the problems of high operating power consumption and high operating costs of the multi-stage refrigerant compressor in the above background art, the present invention aims to provide an improved refrigerant compression system and method that can significantly reduce energy consumption.

[0005] The present invention provides a system for reducing the energy consumption of a multi-stage refrigerant compressor. The compressor (1) at least includes a first compression section composed of a first compression stage and a second compression stage connected in series. An inter-stage cooling device is provided between the outlet of the first compression stage and the inlet of the second compression stage.

[0006] Further, the inter-stage cooling device is a water cooler.

[0007] Further, the water cooler is a shell-and-tube heat exchanger. The refrigerant discharged from the first compression stage is passed through the tube side, and circulating cooling water is passed through the shell side.

[0008] Further, an elastic support structure is provided on the refrigerant pipeline connecting the inter-stage cooling device.

[0009] A method for reducing the energy consumption of a multi-stage refrigerant compressor, which is applied to the system described in any one of claims 1 to 4. The method is as follows: Compress the refrigerant through the first compression stage; Introduce the refrigerant discharged from the first compression stage into the inter-stage cooling device for cooling; Feed the refrigerant cooled by the inter-stage cooling device into the second compression stage for compression.

[0010] Further, cool the temperature of the refrigerant from 97°C to 48°C.

[0011] The beneficial effects of the present invention are as follows: Compared with the prior art, by adding a cooling device at a specific inter-stage (between the first stage and the second stage) of the multi-stage compressor, the present invention directly reduces the temperature of the refrigerant entering the subsequent compression stage, achieving a significant reduction in the total power of the compressor. According to the implementation data, this improved solution can reduce the full-load power of the compressor from approximately 6900 KW (simulated value) or 6700 KW (design value) to approximately 6000 KW, saving a large amount of electric energy per hour (such as 700 degrees of electricity), greatly reducing the long-term operating costs of facilities such as LNG storage and distribution depots, with remarkable energy-saving effects and high economic benefits and popularization value. At the same time, the consideration of pipeline support also ensures the stability and reliability of the retrofitted system. Description of the Drawings

[0012] Figure 1 It is a system block diagram of the background technology of the present invention; Figure 2 It is a system block diagram of the present invention. Detailed Embodiments

[0013] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings of the specification and the specific embodiments.

[0014] Embodiment 1: The present invention will be further described in detail below with reference to the accompanying drawings and specific cases. An embodiment of the present invention is applied to a set of refrigerant compressors in the Guizhou Zunyi LNG storage and distribution depot project. The compressor is manufactured by Wuxi Compressor Co., Ltd. and is designed to operate in four stages and two sections. The first section includes the first stage and the second stage of compression, and the second section includes the third stage and the fourth stage of compression.

[0015] In the original design of the present invention, after the refrigerant is compressed in the first stage, it directly enters the second stage of compression. At this time, the temperature at the outlet of the first stage is approximately 97°C, and the total power of the compressor (1) is relatively high, with a simulated operating value of approximately 6900 KW.

[0016] Refer to Figure 2, the original system was improved. Inside the first compression stage, specifically between the outlet pipeline of the first compression stage and the inlet pipeline of the second compression stage, a new water cooler (inter-stage cooling device 2) was connected by adding pipelines for extraction and introduction. This water cooler is a shell-and-tube heat exchanger, with specific parameter examples: weight 6180 Kg, heat transfer area 142 ㎡, length 5.2 meters, and diameter 0.9 meters. The tube-side medium is a mixed refrigerant, with a design pressure of 2.5 MPa; the shell-side medium is circulating water, with a design pressure of 1.6 MPa. This water cooler is installed on a bracket above the steel structure, maintaining a certain distance (about 3.44 meters) from the compressor 1 body, and is about 3.7 meters above the ground, and is connected to the steel structure by bolts. The refrigerant inlet and outlet pipelines connecting the water cooler are supported by independent brackets. To handle the stress problems that may arise due to the newly added pipelines, elastic supports are specially set on the refrigerant-side pipelines to adjust the pipeline stress during installation and commissioning. After the stress is adjusted appropriately, the elastic pins are removed to ensure the stable operation of the compressor 1 and avoid noise or unstable flow.

[0017] Example 2: A method for reducing the energy consumption of a multi-stage refrigerant compressor, the method being: compressing the refrigerant through the first compression stage; introducing the refrigerant discharged from the first compression stage into the inter-stage cooling device 2 for cooling; and sending the refrigerant cooled by the inter-stage cooling device 2 into the second compression stage for compression.

[0018] Furthermore, the temperature of the refrigerant is cooled from 97 °C to 48 °C.

[0019] Through this newly added water cooler, the refrigerant at the first-stage outlet is forcibly cooled. During operation, the first-stage outlet temperature is effectively controlled at around 48 °C. The cooled refrigerant with a significantly reduced temperature (about 48 °C) then enters the second compression stage. Since the temperature of the refrigerant entering the second stage drops significantly, the compression power consumption of the second stage and the subsequent third and fourth stages also decreases accordingly, ultimately resulting in a significant decrease in the full-load total power of the entire compressor 1. According to the actual operation effect, the full-load power reaches about 6000 KW, which is about 900 KW lower than the original simulation value and about 700 KW lower than the contractually agreed value.

[0020] Calculated based on an annual operation of 8000 hours and an electricity price of 0.6 yuan per degree, compared with the contractually agreed value (6700 KW), the annual electricity savings are approximately (6700 - 6000) KW * 8000 h = 5.6×10^6 degrees of electricity, and the electricity cost savings are approximately 3.36 million yuan. The energy-saving and cost-reducing effects are very significant.

[0021] This example proves that the technical solution of adding an inter-stage cooling device 2 between the first stage and the second stage of the multi-stage refrigerant compressor proposed by the present invention is a practical technology for effectively reducing the energy consumption of the compressor and saving operating costs.

[0022] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A system for reducing energy consumption of a multi-stage refrigerant compressor, the compressor (1) comprising at least one first compression section consisting of a first compression stage and a second compression stage connected in series, characterized in that: An inter-stage cooling device (2) is provided between the outlet of the first compression stage and the inlet of the second compression stage.

2. The system according to claim 1, characterized in that The interstage cooling device (2) is a water cooler.

3. The system according to claim 2, characterized in that The water cooler is a shell and tube heat exchanger, the refrigerant discharged from the first compression stage is introduced into the tube side, and the circulating cooling water is introduced into the shell side.

4. The system according to claim 1, characterized in that A refrigerant pipeline connected to the interstage cooling device (2) is provided with an elastic support structure.

5. A method for reducing energy consumption of a multi-stage refrigerant compressor, applied to the system according to any one of claims 1 to 4, characterized in that: The method comprises: compressing the refrigerant through the first compression stage; introducing the refrigerant discharged from the first compression stage into the interstage cooling device (2) for cooling; and sending the refrigerant cooled by the interstage cooling device (2) into the second compression stage for compression.

6. The method according to claim 5, characterized in that The temperature of the coolant was cooled from 97°C to 48°C.

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