78- Discussion on the technical design of the vane separator demister for the flash regeneration of rich gas recovery project in natural gas processing plants

As is well known, the rich gas generated by the flash regeneration of the rich liquid in acid gas absorption towers generally contains a large amount of liquid droplets and foam, and its pressure is not high. For the effective recovery and utilization of rich gas, it is often necessary to subject the gas that has been regenerated through flashing to a pressurization cycle; compressor units are required to carry out the effective pressurization of this gas.

The rich gas generated by flashing, which contains numerous liquid droplets and foam, can cause serious damage to the proper operation of the rich gas recovery compressor. In the past, owners and design firms did not pay enough attention to the gas-liquid separation and foam removal process at the compressor inlet, which led to liquid accumulation in the intake pipelines and frequent compressor failures. This not only resulted in poor operational performance but also increased the maintenance costs for the compressor’s core components. Therefore, owners and design firms have carried out process modifications to the vapor-rich recovery compressor inlet gas-liquid separators and demisters that were originally installed or newly built.

Taking the renovation project of the rich gas pressurization and recovery process at a natural gas processing plant in a certain northwest natural gas field as an example, this paper analyzes and discusses the technical design issues related to the demister in the compressor inlet gas-liquid separator.

The components of the enriched gas resulting from flash regeneration at this natural gas processing plant are as follows: Component, Composition, mol%; Range of mol%. CH4: 60.90405, 59.15–70.93; C2H6: 22.69626, 18.4–25.3; C3H8: 11.30422, 9.23–13.50; I-C4H10: 1.737745, 1.2–2.1; N-C4H10: 1.21678, 0.9–1.5; I-C5H12: 0.002345, 0.001–0.004; N-C5H12: 0.12289, 0.1–0.2; C6+: 1.1614, 0.8–1.5; N2: 0.33609, 0.20–0.6; CO2: 0.312377, 0.2–0.4; H2O: 0.205686, 0.1–0.4; H2S: 0.000178, 0.0001–0.0002

The operating conditions are as follows: 1) Inlet pressure: 0.6 MPa (g); 2) Inlet temperature: 30–40°C; 3) Natural gas flow rate: 5×104 Nm3/d; 4) Separation precision: 99% efficiency in separating liquid and solid particles of 5 μm and larger size.

This post was last edited by luoli519 on 2023-9-27 at 16:00. Regarding the separation technologies and equipment used to remove liquid droplets, foam, and small amounts of solid particles from the natural gas entering the compressor, these include filter-coalescer separators, multi-factor cyclone separators, vane separators, fiber or mesh-based separators, as well as separation tanks that rely solely on gravity for separation. Which separator is suitable for the aforementioned operating conditions?

This post was last edited by luoli519 on 2023-9-27 at 16:01. Based on our many years of experience in the design and operation of equipment for dynamic separation technologies in domestic and international projects, we offer the following suggestions: 1. Pure gravity-based sedimentation separation tanks are not suitable. Due to the high flow rate of the rich gas, according to the law of gravitational sedimentation, even a separation tank required to settle particles of around 100 microns in size would have to be very large; this results in high manufacturing costs for the tank’s structure, as well as low separation efficiency. 2. Fiber mesh separator: usable, but not very suitable. Since the inlet gas comes from the flash regeneration of the rich liquid in the absorption tower, the gas phase contains highly viscous hydrocarbons and paraffins, which can cause rapid clogging of the fiber mesh internals. Therefore, these internals need to be replaced regularly, and spare units as well as spare parts are required. The operating and maintenance costs are high, and the amount of maintenance work is substantial. It is also not suitable for conditions with large fluctuations. 3. Feather leaf separator: usable and suitable. This vane separator is the fifth-generation high-efficiency separator, and its excellent technical performance in terms of quantitative separation efficiency, operational flexibility, operating pressure drop, anti-clogging capability, and stability represents a substantial improvement over the first-generation Chevron flat-plate baffle separators; as a result, it is widely used in various gas-liquid separation applications both domestically and internationally. In particular, the feather-leaf separator boasts comprehensive advantages such as excellent anti-clogging performance, a very wide range of operational flexibility, low operating pressure drop, precise separation, no need for a backup unit, and extremely low operating and maintenance costs – advantages that are difficult for other types of separators to match. Under the low-pressure conditions here, the performance can be fully utilized. 4. Multi-factor cyclone parent-child separator: usable, but the cost-performance ratio is not very favorable. Under medium and low pressure conditions, the cost of the internal components for multi-factor cyclone mother-son separators is higher than that of the internal components for vane-type high-efficiency gas-liquid separators, thereby reducing the cost-effectiveness advantage of multi-factor cyclone mother-son separators. The multi-factor cyclone mother-son separator boasts significant advantages in gas-solid separation, as well as gas-liquid-solid separation under high-pressure and ultra-high-pressure conditions. The multi-factor swirl parent-child separator has a higher operating pressure drop compared to the vane-type high-efficiency gas-liquid separator, and it is not very suitable for use in situations with large fluctuations in operating conditions. 5. Filter-coalescer separator: usable, but the cost-performance ratio is not favorable. The fundamental working principle of the internal components in the filter-coalescer separator is similar to that of fiber meshes; these components are prone to being clogged by highly viscous paraffin asphaltenes carried by air currents, requiring regular replacement. Additionally, spare units and spare parts are necessary. Operation and maintenance costs are high, and the amount of maintenance work is substantial. Unless used for precision separation in high-value-added applications.

This post was last edited by luoli519 on 2023-9-27 at 16:01. The G50 type vane separator provided by our company for the aforementioned project is as follows: 1. Model number: NOVEL G50-31-116.03； 2. Housing: Dimensions ID32"*TL/TL 142", made of SS304, 150# ； 3. Inner components: Model G50-11-250-EDP, an inner component set featuring the fifth-generation G50 patented airfoil separation technology, made of SS304 material ； 4. Separation efficiency: 4N level removal of particles with a size of 5 microns or larger; the residual amount of such particles in the gas produced is less than 0.1 G/MMSCF ； 5. Overall operating pressure drop under rated load: not more than 0.10 psi.

I think the rich gas can be separated using a separator, and the resulting gas can be used in boilers, heating furnaces, and so on

This post was last edited by luoli519 on 2023-9-27 at 16:01. Recently, NOVEL’s official website www.novelseparationtech.com uploaded the following content: 1. Drawings of the paraglider-type separator； 2. Fluidized bed gas-solid separator drawings ；