Sunday, January 25, 2015

Gas Separation Membrane Technology Saves Energy And Conserves Resources

By Janine Hughes


Around 35 years ago a new industry was born that has developed advanced ways to separate the components of gases. The process is becoming increasingly important as a way to save production costs while producing less environmental pollution, and is still in its infancy. What began as experiments in diffusion has led to the emergence of processes being widely used today, and gas separation membrane technology is developing rapidly.

The major focus is now on removing hydrogen in ammonia production facilities and petrochemical plants, taking carbon dioxide and water vapor out of natural gas during refinement, in scrubbing nitrogen from the air, and separating organic vapors from other gases. In the past, filters have been used successfully to filter out the components of liquids, and the same general principles of that technology also apply to gases.

The newer processes have become especially significant within the petrochemical industry, and are now cost-competitive with other methods. Extracting various valuable components from natural gas has been historically expensive, but can now be removed quickly and efficiently without incurring extra costs. The associated equipment is relatively simple to use, and is considered low-maintenance. Related sales are in the multi-miillion dollar range.

The key to efficient success in this process is the membrane itself. Materials used to make them may differ, but all capitalize on the advantages of using a selectively permeable barrier. Each is designed to permit different types of materials, including gases, liquids, and vapors, to pass through at different rates. This effectively restricts the molecular flow, and prevents some from crossing the barrier at all.

Polymers are the most common materials used to make these filters. This form of plastic can be fashioned into hollow fibers that have a large surface dimension when made into a filter. They are made using existing manufacturing technology, which keeps production costs at a reasonable level. Current technology is advanced enough to make large-scale production for industry practical.

The process can be used continuously, and generally uses a high-pressure stream of the gas mixture. It is forced to pass by the membrane, and certain types of molecules are released on the other side, while others are prevented from passing. Those that cannot can be retained as well, and the efficiency of this method is determined by the properties of the permeable barrier.

The advantage of using this method is the removal of a major production step that must be taken when using older technologies, such as condensation, cryogenic distillation of air, or amine absorption. All those methods require a gas-to-liquid phase change, and that extra requirement generates significant costs. The use of membranes eliminates that portion of the process, and reduces production expenses over time.

The petrochemical industry today is thriving, but must always continue to search for new methods of production that make the best use of dwindling supplies of raw materials. The future of this technology is bright, with new applications targeting the separation of propylene from propane, or the extraction of hydrocarbons from methane or hydrogen. Expansion during the next decade promises to be steady.




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