ExxonMobil has completed of an expansion to a carbon capture plant
using its Controlled Freeze Zone capture technology near LaBarge, Wyoming. The $86-million expansion includes the installation of compressors to capture 50% more carbon dioxide for potential use in enhanced oil recovery and other industrial uses. In 2008, ExxonMobil captured nearly 4 million metric tons
of CO2 at LaBarge.
|Simplified view of CFZ. Click to enlarge.|
With the expansion, the plant has the capacity to capture approximately 365 million cubic feet per day of carbon dioxide from the gas streams—equivalent to the amount emitted by more than 1.5 million cars.
In a separate project in Wyoming, ExxonMobil is developing Controlled Freeze Zone (CFZ) technology for carbon capture. Most current capture technologies use a solvent to remove CO2 from the gas stream, but CFZ is based on the freezing and re-melting of CO2 in a modified distillation column. CFZ technology works by removing CO2 and hydrogen sulfide (H2S) from natural gas in a specially-designed section of a distillation tower, where CO2 is allowed to freeze in a controlled manner.
Next, CO2 is remelted and further distilled to recover valuable methane. It can then be pumped safely for injection into dedicated wells—either for sequestering or for use in enhanced oil recovery. The remaining natural gas now contains the desired level of purity.
In conventional methods, CO2 is separated at very low pressure and must be compressed at significant costs for injection into underground storage. In contrast, the CFZ technology discharges the CO2 as a high pressure liquid, offering a strong commercial advantage. As a result, says ExxonMobil, the CFZ technology could make carbon capture and storage more economical.
CFZ was developed by ExxonMobil Upstream Research Company and has undergone significant improvements since the 1980s, when, in an industry first, it proved the concept of freezing carbon dioxide in natural gas separation with a CFZ pilot plant.
The captured carbon dioxide at LaBarge is sold to companies for enhanced oil recovery. Enhanced oil recovery involves the injection of carbon dioxide into reservoirs to produce additional oil and gas. The carbon dioxide for this project is captured from the natural gas streams produced from fields in Wyoming. The gas streams contain significant amounts of carbon dioxide and other components that are removed at the LaBarge processing plant.