Gas Processing Facilities 101

Cryogenic processing plant (aka striping plant) is a facility where natural gas flowing from wells is cooled to sub-zero temperatures in order to condense liquids or NGLs (natural gas liquids). These can include butaneethane and propane. NGLs are shipped to market and often used in refineries and petrochemical plants for fuel or feedstock. The methane gas that remains after removing liquids is transported via pipeline to where it is needed.

As an example of how cryogenic processing works, gas in Butler Co., PA typically has a BTU level that runs around 1250. A higher BTU level signifies the presence of greater amounts of NGLs. A cryogenic plant reduces the BTU level of the gas flowing from the well to 1100 which is a suitable level for use as natural gas.

Typically a plant separates NGLs from natural gas by chilling the gas stream down to around -120 degrees Fahrenheit. This allows a blended liquid hydrocarbon feedstock to be collected which then is fed into a fractionation plant that finishes processing the liquid hydrocarbon or Y Grade into high purity propane, butane and natural gasoline.

Fractionator  Producers transport natural gas through pipelines directly from the well to the processing plant. Their goal is to collect the natural gas produced in a region and separate the various gas components. They are then stored, transported and sold. Fractionators have several means of separating the components, but one of the most efficient is with the use of refrigeration, at cryogenic temperatures (-238 F). At this low temperature, gaseous methane can be separated from the liquefied ethane and heavier hydrocarbons by distillation. Further distillation then separates ethane from the propane and heavier hydrocarbons.

Cracker  A cracker plant looks similar to a gasoline refinery, with miles of pipes and large storage tanks. The final complex could cover several hundred acres. This plant would take the ethane separated out of the natural gas stream from the wells in a fractionator and convert it to a more valuable chemical, ethylene. The plants are called crackers because they use heat and other processes to break the ethane molecules into smaller chemical components.

How do we use ethylene? Ethylene is a component of plastics. You probably note as you recycle plastic bottles HDPE and LDPE, components of plastics, products of ethylene.