Monday, January 26, 2015

Gas Separation Membrane Technology Is More Energy Efficient

By Janine Hughes


Nearly four decades ago a fledgling industry emerged that specializes in developing advanced methods of separating the individual components of gases. Today, those efforts have become an important factor in driving production costs lower by using less energy, and eliminating some types of environmental pollution. Early experiments in diffusion led to practical industrial applications today, and gas separation membrane technology is rapidly expanding.

The primary impact is in hydrogen separation in petrochemical plants or ammonia production facilities, in removing nitrogen from air, separating water vapor and carbon dioxide from natural gas during refining, and the removal of organic vapor from air or other gas mixtures. Various types of filters have separated liquid components successfully, and the same general filtering principles are being applied to industrial 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.

The most common materials used in membrane separation of gases are polymers, which can be transformed into into fibers that are hollow and have a relatively large surface area. They are made from currently existing materials using available technology, and the cost of manufacturing is comparatively low. The technology is now suitable for large scale industrial production of various types.

A stream of a gas mixture under high pressure can be passed through the filtering system continuously. As it is forced through a filtering system various specific molecules are released on the far side, while others are retained and can also be used, reducing waste. The process of separation varies, but in general is determined by the properties of the membrane barrier itself.

The most attractive advantage associated with this process is the removal of a major step in production that is characteristic of more established technologies, which include cryogenic distillation of air, amine absorption, or basic condensation. The older processes all include a phase where gas converts to liquid, a step that necessarily uses more energy and is costlier. Membranes eliminate that effort at significant cost savings.

Because the petrochemical industry must continuously find new ways to produce fuels and other products in a way that makes the best use of existing raw materials, the future of this type of technology is open-ended. New applications can be applied to growth areas such as the removal of hydrocarbons from hydrogen or methane, or propylene from propane. Expansion in the next two decades promises to be continuous.




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