Carbon Molecular Sieve and Producing Nitrogen Lasers

First invented in 1960 the laser was first called the solution looking for a problem.  More than fifty years later lasers have become an invaluable part of human technology. Today uses for lasers range from being used in material processing endeavors such as laser cutting, welding, and bending, to reading bar-codes when you purchase something at a store, to being used by the military as a  targeting sight, and even being used to do surgery (laser eye surgery being the one of the most common).

As technology has improved many different types of lasers have been developed.  One of the more common types of lasers developed was the nitrogen laser.  This laser uses nitrogen as a medium and an electrical discharge to create its beam.

Nitrogen lasers are particular useful in handling material processing functions for example they are good at cutting metal.  However material processing functions require that lasers be efficient and cost effective and that is where nitrogen generation systems play an important role.

In order for the laser to function it needs pure nitrogen (between 97%-99.99%).  The most common type of technology used in purifying nitrogen is membrane technology.  This method is able to produce nitrogen up to 99%.  However if that amount of nitrogen purity is not enough to generate a laser.  Depending on what you are using the laser for the nitrogen may not be purified enough.

In order to get the purest form of nitrogen a PSA system and a carbon molecular sieve is needed.  The PSA system, air compressor, and carbon molecular sieve work  when the air compressor forces compressed air into the PSA system.  Naturally compressed air is composed of 78% nitrogen, 21% oxygen, and less than 1% of various other gases, the same air that makes up the air in our atmosphere.

Once this air enters the PSA system the carbon molecular sieve adsorbs all of the oxygen and other gases, the nitrogen is able to pass by because it is not attracted to the carbon molecular sieve and it is then guided into a storage tank (See our earlier article on adsorption with carbon molecular sieve).  Once the carbon molecular sieve reaches its adsorption capacity it can be regenerated so that it can be used over and over again.

The end result of this is process is that you have now produced nitrogen that is between 99%-99.99% pure.  This highly pure form of nitrogen is useful for cutting through tougher and thicker metals.

Sources:

http://www.thefabricator.com/article/lasercutting/a-case-of-the-gas

http://inventors.about.com/od/lstartinventions/a/laser.htm

http://www.megacarbon.com/techlit/carmolsiv.pdf

What Is It and How Does It Separate Oxygen from Nitrogen

What is carbon molecular sieve?

Carbon molecular sieve is an adsorbent that fuses the ideas behind both activated carbon and zeolites into one product.  Activated carbon is known for its high porosity and zeolites are known for their ability to be crafted into highly specialized adsorbents called molecular sieve.  Carbon molecular sieve is a product that brings the benefits of both of these products together.

Carbon molecular sieve is made out of coal (the same material most activated carbon is made out of) and it specializes in adsorbing material under 10 angstroms, something activated carbon can not do accurately.  The smallest pore size created for carbon molecular sieve is 4A, but it exists in a 5A, and 10A (or 13X) as well.

Carbon molecular sieve specializes in separating oxygen from nitrogen, an important part in natural gas processing. This process is done with a PSA (Pressure Swing Adsorption) device in two phases.  The first phase sees the gas enter the PSA generator and the oxygen is adsorbed while the nitrogen passes through because the nitrogen molecules are too large and are used as a separate product.  The second phase sees the oxygen slowly released from the sieve at low pressures and thereby regenerating it so that the separation process can be repeated.

Carbon molecular sieve is used in this situation as opposed to activated carbon because the physical size between oxygen (0.28nm×0.40nm) and nitrogen (0.30nm×0.41nm) molecules are so close.  The pore sizes on carbon molecular sieve are able to accommodate these small size differences, where as activated carbon would just end up adsorbing both of them.

Molecular sieve isn’t used because it is a polar adsorbent, meaning its surface area attracts other polar molecules.  Oxygen is a non-polar molecule and would be attracted to other non polar surfaces.  Carbon molecular sieve is one of the few non-polar adsorbents out there which is why it is chosen over molecular sieve for this application.

In addition to separating nitrogen from oxygen carbon molecular sieve can be used for metal heat treatment, electron production, and as preservative in food products.