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Fractionator? Cracker? What are They?

Posted: April 15, 2012

With the recent report that a site has been selected along the Ohio River in the Beaver County community of Monaca for a “cracker plant,” what does that mean?

Shell Oil has indicated that they are going to begin the process of the feasibility of construction, to perform the due diligence to determine if an “ethane cracker” might be situated at this industrial site. This is all the result of the unconventional shale natural gas drilling activity in PA, WV, and OH.

 The two shales most drilled to date, Marcellus and Utica, often contain components other than methane (natural gas). Some areas of western and southwestern PA produced natural gas that also contains propane, butane, and ethane. These will raise the BTU value of the gas being produced above the standard that flows in pipelines. For this reason they must be separated from the methane. As a bonus, these components, once separated out, have a ready market waiting to purchase them, adding value to the gas produced from each well.

Fractionator  Several gas processing plants, or fractionators, have been constructed in western PA. 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  Now it’s time for the ethane 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.

submitted by Jon Laughner, Penn State, Beaver County Educator