ExxonMobil scientists invented and patented the Controlled Freeze Zone™ technology, a breakthrough process that more efficiently removes impurities from natural gas. The CFZ™ technology could also make carbon capture and storage more affordable and efficient in reducing greenhouse gas emissions. The technology is fully developed and qualified for commercial application.
This proprietary CFZ™ technology targets the significant portion of today’s world gas resources which contain large amounts of carbon dioxide (CO2). While conventional technologies are unable to efficiently process natural gas with large concentrations of CO2, the CFZ™ technology has the ability to process natural gas with a wide range of impurities. The application of the CFZ™ technology at a global scale could therefore expand the pool of affordable clean-burning natural gas resources for development and delivery to consumers.
The CFZ™ technology efficiently removes impurities from natural gas and is less expensive than existing technologies, requiring fewer processing steps and equipment. This increases its attractiveness, especially for offshore and remote applications.
The 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 melted 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 discharged 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, the CFZ™ technology could make carbon capture and storage more economical.
The benefits of CFZ™ technology
The CFZ™ technology offers the following advantages relative to conventional gas treating processes for the removal of CO2 and H2S in natural gas:
Single step processing
- Meets natural gas pipeline quality requirements without additional polishing
- Requires no solvent regeneration, additive recovery or downstream dehydration facilities
No limit on CO2 or H2S content
- Handles highly sour gases with ease
- Easily accommodates increases in feed concentration of sour gas components over the life of the facility
- Its cost advantage over competing technologies expands with increasing acid gas content
High pressure operation
- Discharges acid gas as a dry non-corrosive high pressure liquid that can be pumped for sequestration or use in enhanced oil recovery
- Reduces compression horsepower and equipment requirements for acid gas injection or enhanced oil recovery
Alternative to sulfur recovery plants
- Discharges H2S and other sulfur compounds with the CO2 for disposal
- Provides an attractive alternative to building expensive, high operating cost sulfur plants
Overall cost savings
- Simplifies process and lowers equipment count, making the CFZ™ technology a low cost alternative
- Reduces fuel gas consumption, allowing greater gas sales revenue — Allows efficient integration of gas treatment, acid gas injection, and/ or power generation operations
