38- Discussion on the selection and design of high-efficiency low-temperature separators for gas well stream dehydration and dehydrogenation systems

This post was last edited by luoli519 on 2019-1-31 at 22:45. Here, a simple flowchart of the dehydration and dehydrocarbonation unit in a natural gas processing plant is provided for everyone to share, analyze, and discuss.

This post was last edited by luoli519 on 2016-10-16 at 15:27. Attached is a simple flowchart of the natural gas dehydration and dehydrogenation unit:

As can be seen from the flow diagram, the pre-cooling separator, also known as the feed gas separator, is primarily used to remove the condensate oil droplets and mist formed in the feed natural gas after passing through the pre-cooler. The post-cooling separator, also known as the low-temperature separator, is primarily used to remove the ethylene glycol/water droplets carried in the gas phase of natural gas after dehydration through ethylene glycol spraying.

Both the raw gas separator and the low-temperature separator are used to efficiently remove liquid droplets and mist carried in the gas stream. Relatively speaking, the amount of liquid droplets and mist formed in the feed gas after pre-cooling is relatively small, whereas the low-temperature separator has to handle natural gas washed with ethylene glycol at a high liquid content. Considering different liquid load conditions in the treated gas stream, the raw gas separator should adopt a vertical structure, while the low-temperature separator should adopt a horizontal structure.

Therefore, it is recommended that design institutes and natural gas processing plants adopt a horizontal structure for low-temperature separators in new projects going forward, replacing the previously used vertical structure. Separators with a horizontal design have a significantly greater liquid storage capacity for the same housing size.

This post was last edited by luoli519 on 2023-10-3 at 14:17. Since natural gas originates from gas collection units, it contains not only condensate and water but also highly viscous gels and particles. For the separation components used in dehydration and hydrocarbon removal units under such conditions, it is recommended to employ dynamic and efficient gas-liquid demisting separation technologies such as multi-factor swirl-type mother-son demisters or vane separators, which offer high separation efficiency and excellent resistance to clogging; traditional mesh-based, filter-based, or cartridge-based demisting components should not be used. The internal components of the latter type tend to clog easily, resulting in high operating pressure drops. Their replacement and maintenance are frequent, which increases operational costs. Additionally, a backup unit is required to be installed so that it can be used as a substitute during filter element replacements.

This post was last edited by luoli519 on 2023-10-3 at 14:17. Moreover, due to changes in the upstream gas collection units and conditions further upstream, there are significant fluctuations in operating conditions. Moreover, the process design conditions differ significantly from the actual operating conditions of the equipment. Therefore, it is necessary to choose dynamic and efficient gas-liquid demisting separators with high operational flexibility, high separation efficiency, and high operational stability, such as the G50 type vane-type separation element or the G54 type multi-factor swirler mother-son separation demisting element. The first generation of Chevron simple light-plate baffles, swirl plates, large-diameter cyclone separators, etc., developed since the mid-20th century, are not very suitable for operating conditions with significant fluctuations.

Generally, triethylene glycol is dehydrated first, followed by pre-cooling and pressure swing separation

This post was last edited by luoli519 on 2016-10-16 19:01. Yes, large and very large natural gas processing plants often use the TEG dehydration process. The TEG dehydration process unit belongs to the tower-based dehydration method; it involves a combination of various towers such as absorption towers, flash towers, regeneration towers, and stripping towers for integrated treatment. This approach is suitable for large-scale and super-large-scale natural gas production and transportation processes, namely projects with a capacity of over 2 billion cubic meters. It is the TEG dehydration method that is used in the dehydration technology we provided for the Xinjiang Xinwen SNG project. In TEG dehydration towers, the operating pressure cannot be too high; otherwise, the wall thickness of the tower equipment will have to be increased, resulting in higher costs. The ethylene glycol-based dehydration process is suitable for high-pressure and ultra-high-pressure conditions at the wellhead, especially for the dehydration and dehydrogenation of natural gas at the wellhead. The equipment can be easily designed as a compact unit, and this process is used in many wellhead gas treatment systems both domestically and internationally. It is not ruled out that improved TEG processes in the future could be used for wellhead gas projects with very high pressures under such conditions.

If time permits in a few days, I will provide the operational parameters of similar projects for everyone’s discussion.