Lab builds distillation test station for energy savings in light hydrocarbon separations

May 6, 2010—In support of its Energy Security mission, the Laboratory is developing methods to increase the energy efficiency of light hydrocarbon separation—the most recent achievement is completion of a sophisticated distillation test station.

Why is this important? Olefins and paraffins (ethylene, propylene, propane, butane, and iso-butane) are the largest commodity chemicals produced in the United States and the world. These hydrocarbon gases are produced as a by-product of petroleum refining and are major feedstocks for the petrochemical industry. Petroleum refining is one of the most energy-intensive industries in the United States. The separation of liquefied petroleum gas (ethane/propane/butane) and olefins (ethylene and propylene) consumes about 400 trillion Btu (British thermal units) per year. Distillation, the primary method for separation, requires equilibrium between the liquid and gas phases. This separation method has low energy efficiency because the relative volatility between separated gases is low. The poor separation efficiency requires the tall distillation columns commonly observed in many chemical plants. 

In collaboration with Chevron, the Lab's Polymers and Coatings Group used hollow fibers as structured packing material to separate iso-butane from n-butane at room temperature. The hollow fibers greatly increase the surface area/volume ratio between the liquid and gas phases and reduce mass transfer resistance in the separation. The hollow fiber column is at least 10 times more efficient than conventional columns.

As a result of the Lab's dramatic increase in separation efficiency, the Department of Energy Energy Efficiency and Renewable Energy-Industrial Technologies Program funded LANL to build a distillation test station to demonstrate that this technology would work on a larger scale under the operational conditions similar to that used in industry. After 14 months of design and construction, the researchers have built a state-of-the-art, computer-controlled test station. Distillation experiments can be performed efficiently and reliably. In addition, the engineers and scientists can conduct the distillation experiments under changeable reflux ratios that interest the industrial partner.

Currently, the researchers are establishing an engineering database with this new test station to provide optimal hollow fiber module design method, flow and pressure parameters, and experience for a pilot plant design. This system can be easily adapted to other types of gas/gas and gas/liquid separation processes using hollow fibers. This research enhances the Lab’s capabilities for applications in energy security, energy efficiency, and CO2 emission reduction.

The team members are Dali Yang (principal investigator), Bruce Orler, and Cindy Welch of Polymers and Coatings; Ron Martinez and Loan Le of Physical Chemistry and Applied Spectroscopy; Vivian Ding of Sensors and Electrochemical Devices; and Wei Qiang of Earth Systems Observations. External collaborators include Chevron, University of Minnesota, and industrial consultant Malcolm Morrison.

Karl Jonietz of Applied Energy is the LANL program manager, and Dali Yang of MST-7 is the technical contact.