85- Feather leaf separators and liquid-liquid separators in the gas-liquid separation of molecular sieve dehydration regeneration gas and oil removal from wastewater in LNG projects

For the gas-liquid separator in the molecular sieve dehydration unit of LNG projects, its main function is to remove the condensate contained in the regenerated gas, preventing this condensate from entering the pipelines and equipment downstream of the regeneration unit. This is done to avoid the accumulation of condensate in those downstream pipelines and equipment, which could lead to flow restrictions as well as operational problems in the downstream equipment, especially the pressure-related equipment. For the liquid-liquid separator used in the molecular sieve dehydration and regeneration process of LNG projects, its main function is to remove combustible light hydrocarbons from the wastewater. This allows those combustible light hydrocarbons to be recovered as fuel. It also helps to reduce the concentration of organic substances such as combustible light hydrocarbons in the wastewater; this not only prevents the volatilization of these hydrocarbons into flammable gases during subsequent processing steps, thereby avoiding safety risks, but also reduces the burden on subsequent wastewater treatment processes and lowers the associated costs.

This post was last edited by luoli519 on 2023-9-27 at 15:16. Regarding the gas-liquid separators used for the dehydration and regeneration of molecular sieves in LNG projects, among the projects that have been built and are in operation in China, some use multi-factor cyclone-type separators, some use vane separators, while others employ fiber-mesh type separators or gravity sedimentation tanks; in fact, some earlier projects did not even have a separator tank for the feed gas before it entered the tower. Regarding the oil removal separators for the gas condensate wastewater generated during the dehydration and regeneration process of molecular sieves in LNG projects, among the projects that have been built and are in operation in China, some use vane-type liquid-liquid separators, while others employ fiber-mesh type liquid-liquid separation tanks; there are even projects that do not have any equipment for oil removal from wastewater.

The multi-factor cyclone parent-child separator belongs to the category of high-efficiency dynamic separation technology equipment. Under the same medium and low pressure conditions, the manufacturing cost of the internal components for multi-factor swirl separator mother-son separators is relatively high, which reduces their cost-performance advantage. The multi-factor swirl separator for mother-son separation boasts outstanding comprehensive cost-performance advantages in gas-solid separation, as well as superior performance in gas-liquid separation under high-pressure and ultra-high-pressure conditions – virtually unmatched by any other alternative.

This post was last edited by luoli519 on 2023-9-27 at 15:17. The feather leaf separator is also a device based on high-efficiency dynamic separation technology; it represents the fifth generation of leaf separation technologies with significant cost-performance advantages at present. The first generation of Chevron vane technology, which was put into use in the mid-20th century, has gone through more than half a century of development, upgrades, and technological improvements, resulting in the fifth generation of vane separation technology. Blades from different technological eras and levels have varying internal structures, and the performance resulting from these structures also differs. The higher the technical level of a blade, the better its overall performance and cost-effectiveness. The vane separation technology has achieved a fundamental improvement in terms of quantitative separation efficiency, operational stability, operational flexibility, anti-clogging performance, and operating pressure drop. Thus, it is widely used under a wide range of operating conditions, such as vacuum, normal pressure, low pressure, and medium pressure.

Regarding the fiber mesh separation tank, it belongs to traditional simple separation technologies and structural separators. It primarily achieves the blocking, interception, and separation of particles carried by the airflow through the \"cells\" formed by the interbridging of fibers within the internal components. On the one hand, due to the slightly different sizes of the \"cells\" formed by the interbridging of fibers, their structure prevents them from being capable of achieving precise separation of small-sized droplets ； On the other hand, the larger droplets formed as a result of interception by the fibrous mesh interior components fall back into the airflow, and gravity settling is required to finally separate them from the airflow, resulting in low separation efficiency. Furthermore, if the airflow contains viscous liquid droplets, foam, and solid dust particles, it is easy for these to block the flow channels in the surface, middle, and deep layers of the fiber mesh internals. In particular, blockages in the middle and deep layers are difficult to remove effectively, requiring regular replacement of the internals; as a result, operational efficiency and maintenance costs are high. In recent years, owners, process package suppliers, and design institutes have increasingly adopted G50 feather-type gas-liquid separation technology and equipment. This technological upgrade replaces traditional fiber-mesh separation tanks, not only improving the efficiency of separation processes but also reducing operational and maintenance costs, thereby securing a technical and economic advantage.

As for gravity sedimentation separation tanks, they are more akin to traditional, simple, and inefficient separation devices. Not only is the separation efficiency low, but the equipment is usually large in size, resulting in high costs for space and piping; the overall cost is even higher when it is installed on a platform. In recent years, owners, process package suppliers, and large and medium-sized design institutes generally no longer use gravity sedimentation separation tank configurations. Only a few small design firms, constrained by their overall technical capabilities and level, still use gravity-settling separation tanks from time to time. Furthermore, for economic reasons associated with the EDP mode, the separation tank is even removed. This requires the technical personnel on the owner’s side to take care of it themselves.

This post was last edited by luoli519 on 2023-9-27 at 15:18. The vaned separators, mesh-type liquid-liquid phase separators, and gravity-driven liquid-liquid phase separators used in the oil removal equipment for the condensate wastewater from molecular sieve regeneration in LNG projects all belong to devices based on kinetic liquid-liquid separation technology. The difference lies in the separation time required for the dispersed droplets in the continuous phase; as a result, the liquid-liquid separation efficiency of these three methods also varies. The order of separation efficiency from lowest to highest is: gravity-driven liquid-liquid two-phase separator

This post was last edited by luoli519 on 2023-9-27 at 15:18. Here, taking an LNG project powered by coke oven gas, designed by a certain LNG technology company in Zhejiang for a client in Shanxi, as an example, we discuss the process and design aspects of vane separators in such separation stages.

The last edit to this post was made by luoli519 on 2017-2-13 at 15:08. Operating conditions for the gas-liquid separator used in the dehydration and regeneration of molecular sieves: 1. Operating pressure: 1.8 BarA； 2. Operating temperature: 40℃ ； 3. Gas phase flow rate: 656 kg/h; 4. Gas phase viscosity: 0.016 cp ； 5. Average molecular weight in the gas phase: 34.98 ； 6. Liquid phase flow rate: 599 kg/h; 7. Density of the liquid phase: 990 kg/m^3; 8. Viscosity of the liquid phase: 0.656 cP ； 9. Surface tension of the liquid phase: 41.5 dyne/cm.

This post was last edited by luoli519 on 2023-9-27 at 15:19. For this application scenario, we employed a G50-type vaned separator; the design results for the gas-liquid separator used in the molecular sieve dehydration and regeneration process, obtained through the NOVEL proprietary precise dynamic separation calculation and design system, are as follows: 1. Separator type: G50-type vaned separator； 2. Separation efficiency: 4N level for removing liquid droplets and foam with a size of 7.7 microns or larger. 3. Overall operating pressure drop: 0.06 kPa. 4. Equipment dimensions: ID700*TL/TL11580.