Managing Waxes and Paraffins
Filtration and Separation Basics by JCI
Separating hydrocarbon liquids from natural gas is common in many compressor stations and processing facilities. The type of filtration and separation equipment used for a given application depends on several factors. A few of these factors include the downstream equipment, droplet size distribution, gas/liquid ratio, flow regime, and desired efficiency.
Standard separators, scrubbers, and filter designs found in these facilities rely on the interception and impaction separation mechanisms to capture and remove liquid particles from a natural gas stream. Consider a Horizontal Inlet Separator or Slug Catcher that is designed to separate natural gas and liquid at the inlet of a gas plant. Hydrocarbon liquid mist is removed using a mesh pad or vane pack mounted near the gas outlet nozzle. Refer to Figure 1 which depicts a standard horizontal separator configuration.
These standard designs are sufficient for many applications, resulting in reliable, efficient separation. However, many liquid-rich natural gas streams contain a wide spectrum of hydrocarbon components. Heavier hydrocarbon components (i.e. waxy hydrocarbon components, paraffins, asphaltenes, or salt) tend to stick to the separation and filtration media. The contaminant builds up over time, resulting in carryover from the separator. The separation device or filter element must be prematurely repaired or replaced — and worse yet, production can be lost to an unplanned shutdown. Refer to the photos in Figures 2a, 2b, 2c, and 2d showing some examples of fouled separation devices and filter media.
Figure 1 - Typical configuration of an inlet separator or slug catcher.
Figure 2a – Damaged mesh pad.
Figure 2b - Plugged mesh pad.
Figure 2c - Plugged vane pack.
Figure 2d - Plugged filter cartridge.
It is not always known in advance whether one of these contaminants will be prevalent. The owner can only rely on their operating experience in a specific formation or with similar facilities. However, if known in advance or if discovered after a facility has been commissioned and in operation, there are designs that can be employed that manage these contaminants, resulting in reliable, low maintenance operation, maximizing production and minimizing operational costs. Refer to Rethink Your 1st Stage Suction Scrubber and Engineering Assessment of an Existing Separator for more information on these designs and on assessing an existing separator.