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Adsorptive Nitrogen Rejection from Natural Gas
Low permeability natural gas reservoirs are being developed across the world using fracturing technologies. The most common approach for fracturing uses water with friction reducing agents and thickening polymers. However this approach requires approximately 400 tanker trucks to bring millions of gallons of water to a well head and results in millions of gallons of contaminated water that must be treated before going back into the natural water cycle. A second approach to fracturing uses high pressure gases such as nitrogen or carbon dioxide. The use of energized fluids such as N2 or CO2 offers the potential to carry out fracturing without the negative aspects associated with water based fracturing. This approach, however, often requires producers to divert initial gas production to a flare until N2 / CO2 gas concentrations in the “flow-back” drop below allowable limits for feeding into the natural gas pipeline network. This project aims to address the loss of hydrocarbon energy and the associated CO2 emissions related to N2 fracture operations by utilizing a new adsorbent developed by Praxair in a modular Pressure Swing Adsorption (PSA) system capable of recovering N2 from produced gas at wellhead locations. Technology development in this area will address the specific problem described above and will shed light on the challenges of modular processing of distributed resources in general.
Reaching total HydroCarbons (THC) target recovery of 55%
Adjusting PSA operations to flow, composition, and temperature variations
Successful design, construction, and control of a modular cyclic system
The adsorbent and pressure swing adsorption system described in this project provides an opportunity to significantly mitigate and even eliminate flaring associated with nitrogen fracturing. By rejecting the N2 from the initial gas flowback streams, hydrocarbon can be recovered from flare and sold to customers. It is estimates that 50 – 80% of the hydrocarbon can be recovered from flare during the flow back operation. This would reduce or eliminate the estimated ~600 kilotons of CO2 emitted annually the USA from current N2 fracking operations. Additionally, this also saves ~20% of the water currently used in hydraulic fracturing by replacing 20% current water fracturing activities with N2.
Georgia Institute of Technology has extensive experience in design and synthesis of functional porous materials for air purification, gas separations, gas storage, and gas capture. Praxair has extensive experience in the design of PSA systems and is equipped with pilot pressure swing adsorption systems at Praxair Technology Center located at Tonawanda, New York.
Project Approved: April, 2017
October 11, 2017