Physical Distribution Management

One company that many do not know about is the air separation industry. This industry is a vital component to everyday life. The process of separating air is a simple process that is dominated by a handful of companies throughout the world, which are as follows: Praxair, Linde, Air Products, Air Liquide, and some smaller companies.

Cryogenic air separation process is one of the most popular air separation process, used frequently in medium to large scale plants. . Cryogenic air separation is a process to produce highly purified gases or liquids and it is done by taking large volumes of air from the atmosphere, which is then compressed, cooled, liquefied. This is then separated into its major components by distillation. After the air is compressed, impurities must be removed. It is the most preferred technology for producing nitrogen, oxygen, and argon as gases and/or liquid products.

The company that we have decided to work with is Linde Gas. Linde Gas started in 1879. Linde Gas has many Air Separation Units (ASU) throughout the world. The Air Separation Unit that we are going to work with is located in Indianapolis. The address of the ASU is 1045 Harding Court, Indianapolis, IN 46217. Our contact's name is Tony Poe. He is the Distribution Manager for the Indianapolis facility and has been with Linde since 1977. This facility was originally owned by Airco Gas, and was acquired by BOC Gases (British Oxygen Company) in the late 80s. In the late 90s Linde Gas purchased BOC Gases.

There are only four main ASU facilities for Linde Gas in the Midwest Region. The following is the list of facilities: Fostoria, OH, Springville, IN (La Porte), Crawfordsville, IN, and Indianapolis, IN

The following are the elements in the atmosphere that make up the air we breathe: nitrogen, oxygen, argon, carbon dioxide, neon, helium, methane, krypton, hydrogen, and xenon. Looking at Figure 1 you will be able to see the process of how Linde is able to take an air compressor and separate the air that we breathe into Nitrogen, Oxygen, and Argon. At the Indianapolis facility they mainly distribute Liquid Nitrogen and Oxygen. The crude Argon that is left over is shipped to another facility to finish processing and then is distributed to customers.

Linde has many different facilities throughout the world. Each facility only makes what gas or liquid that is required by their customers. Linde has the ability to separate the air into each one of these gases but they require different steps of separation. The following is an example of how the air separation is completed at the Linde ASU in Indianapolis, IN.

The first step in any cryogenic air separation plant is filtering and compressing air. After filtration the compressed air is cooled to reach ambient temperature by passing through air-cooled or water-cooled heat exchangers. After each stage of cooling and compression, condensed water is removed from the air.

The second step is removing the remaining carbon dioxide and water vapor, which must always be removed to satisfy product quality specifications. The carbon and water vapor needs to be removed before the air enters the distillation portion of the plant.

This portion of the process is where very low temperatures can make the water and carbon dioxide freeze, which can be deposited on the surfaces within the process equipment. There are two basic methods to get rid of water vapor and carbon dioxide, which are molecular sieve units and reversing exchangers. The Linde plant has a reversing exchanger process.

The third step in the cryogenic air separation is the transfer of additional heat against product and waste gas to bring the air feed to cryogenic temperatures. The cooling is usually done in brazed aluminum heat exchangers, which lets the heat exchange between the incoming air feed, cold product and waste gas streams leave the air separation process. The very cold temperatures required for distillation of cryogenic products are formed by a refrigeration process comprising expansion of one or more elevated pressure process streams.

The fourth step involves the use of distillation columns to separate the elements into desired products. For example, the distillation system for oxygen has both "high" and "low" pressure columns. Nitrogen plants can have one or two columns. While oxygen leaves from the bottom of the distillation column, nitrogen leaves from the top. This is all based on the elements boiling point. Argon has a boiling point similar to that of oxygen and it stays with the oxygen. If however high purity oxygen is needed, it is necessary that at an intermediate point argon must be removed from the distillation system. Plants which produce high purity oxygen, nitrogen or other cryogenic gases require more distillation stages.

The fifth and final stage involves refrigeration