48- Feather vane separators in the design of mixed refrigerant cycle compressor systems and absorption systems in LNG plants

This post was last edited by luoli519 on 2017-3-4 at 14:54. Regarding the high-efficiency gas-liquid separators (MRC Suction Scrubbers) that need to be installed in mixed refrigerant compression systems, process design typically involves a first-stage MRC compressor inlet high-efficiency gas-liquid separator, a second-stage MRC compressor inlet high-efficiency gas-liquid separator, as well as a high-efficiency gas-liquid separator in the discharge section (MRC Suction Scrubber).

In a 2-stage mixed refrigerant compression system, the high-efficiency separator at the inlet of the 2nd stage MRC compression unit serves a dual role: it functions as both the high-efficiency separator at the outlet of the 1st stage MRC compression unit and the high-efficiency separator at the inlet of the 2nd stage MRC compression unit; in essence, it acts as a separator between the MRC compression stages.

The last edit to this post was made by luoli519 on 2016-11-12 at 14:33. The main function of a gas-liquid efficient separator in a mixed refrigerant compression system is as follows: 1. At the inlet of each compression unit, it removes liquid refrigerant from the incoming airflow, preventing the liquid phase from entering the compressor. This avoids difficulties in compression, increased power consumption, excessive temperature rise, and even damage to the compressor’s core components due to liquid slugging； 2. At the outlets of each compression unit, the liquid refrigerant is separated from the gas stream in a timely manner; the refrigerant is used solely to cool the gas phase, thereby preventing it from being wasted on cooling the liquid, which results in significant energy savings ； 3. The compressor inter-stage separator serves both as an inlet separator and an outlet separator ； 4. In addition, this separator also has anti-surge, noise-suppression, and buffering functions.

The last edit to this post was made by luoli519 on 2023-10-3 at 10:15. In the mixed refrigerant compression units of LNG plants, precisely designed vane separators play a significant role in reducing design redundancy in MRC compressor systems, thereby saving costs; they also help to decrease the amount of refrigerant required and the electrical energy consumed for compression； As for the technical upgrading of old devices, it can significantly increase the production capacity of the original compression equipment. Therefore, whether they are owners of new projects or existing facilities, or EPC contractors for LNG projects, all pay great attention to the installation of such vane separators.

In traditional LNG plant refrigerant compression units, the buffer separation tank is usually a hollow tank without any components based on dynamic separation technology; its main function is to act as a buffer at the inlet. The separation of liquid droplets and mist by gravity is ineffective, especially under conditions of high gas flow rates, which results in the airflow entering the compressor containing a large amount of liquid droplets and mist. When selecting compressors, the design team is forced to choose larger models based on principles of safety and reliability, which results in high investment costs for the compressors. Due to the large amount of liquid in the intake air, the compressor consumes more power, experiences frequent operational failures, resulting in high project costs.

Traditional compressor inlet buffer tanks have not led designers and owners to fully recognize their importance; they are often provided by the compressor manufacturers as an optional feature, with little effect on gas-liquid separation, and sometimes they even fail to fulfill their buffering function properly.

This post was last edited by luoli519 on 2023-10-3 at 10:17. Regarding the vane separators that need to be designed for the MRC of the mixed refrigerant compression system in LNG plants, their structural forms vary depending on the installation location. Generally speaking, for the first-stage MRC inlet gas-liquid high-efficiency separator, it needs to be designed as a horizontal structure with internal baffle separation components; this is because the first-stage MRC inlet gas-liquid high-efficiency separator must hold a large amount of liquid refrigerant, and a horizontal structure is more appropriate in such cases ； As for the high-efficiency gas-liquid separator between stages and the high-efficiency separator in the discharge section, they are usually designed as vertical structures with built-in baffle separation internals, mainly because this approach offers advantages in terms of floor space required and piping costs.

This post was last edited by luoli519 on 2016-11-12 at 19:37. Taking as an example the high-efficiency gas-liquid separator in the inlet section of the first-stage compression unit of the mixed refrigerant compression system for a renowned foreign project that processes 3 million standard cubic meters of LNG per day, the operating parameters are as follows: 1. Fluids: N2, CH4, C2H4, C3H8, C5H12; 2. O.P.: 391 kPaA; 3. O.T.: 18℃； 4. Gas phase flow rate: 81,430 Am^3/h, MW=33.71, viscosity 0.011 cp, density 5.6 kg/m^3; 5. Liquid phase flow rate: 50 Am^3/h, viscosity 0.2 cp, density 623.8 kg/m^3.

This post was last edited by luoli519 on 2023-10-3 at 10:17. The technical requirements for the gas-liquid efficient separator in the inlet section of the MRC stage 1 compression unit, as specified in this internationally renowned LNG process package, are as follows: 1. Separation efficiency: 4N level, 2 microns； 2. Operational flexibility: 50%~110% ； 3. Separator type: Horizontal ； 4. Type of internal separation element: G50 type vane separation element set + PAD ； 5. Material: SS304L.

This post was last edited by luoli519 on 2016-11-12 at 19:22. The schematic diagram of its process package is also listed here as follows: