What are the Different Ways of Getting Nitrogen or Oxygen for Your Business?

Industrial Gases Compressed Air Wiki Nitrogen

When you need a supply of an industrial gas like nitrogen and oxygen for your business, the first solution that probably comes to mind is to get it delivered to you in bottles. However, there are a lot more, possibly more efficient, options to consider. In this article we will talk about obtaining nitrogen in bottles, but also in liquid form and by making your own with a PSA or membrane nitrogen generator.

Obtaining your nitrogen through a third party supplier

Bottled Nitrogen

A first option is to buy bottles of nitrogen from a nitrogen producer. This process is very straightforward: You order the desired nitrogen quantity for your application and the supplier delivers it to you in big heavy bottles. N2O2, generated by a cryogenic nitrogen plant, is converted into a gas and bottled under very high pressure (300 bar). This means a lot of nitrogen gas can be stored in a relatively small bottle. However, in order to withstand the high pressure, the walls of the receiver are very thick. These bottles are placed in a rack and get transported to their destination on trucks. After use, the emptied bottles are collected by the gas company.

Advantages: Disadvantages:
  • If your nitrogen consumption is relatively low, it is a very easy solution.

  • Since the nitrogen you have is readily available, peak flows are allowed.

  • The installation is very simple.

     

     

     

  • Since the bottles are made of thick, heavy steel (and nitrogen is nearly weightless), the gas company is basically transporting iron, which is very environmentally unfriendly.
  • The bottles can never be fully emptied. If the working pressure is 10 bar, you will only be able to get the nitrogen out when the pressure in the bottle is more than 10 bar. The ‘rest’ gas stays in the bottle and returns to the gas company when the ‘empty’ bottles are picked up.

  • The price is comparatively high because of the effort the gas company has to put into getting the nitrogen to you. After generating the gas, they compress it, transport the heavy iron bottles to you and pick them back up when they are empty.

  • A special bottle rack switching system is required if interruption of production process is not allowed.

  • Safety concerns (heavy steel handling, high pressure)

  • You are very dependable on your nitrogen supplier.

  • Not suitable for high gas consumptions

Liquid Bulk Nitrogen

A second option is to install a liquid nitrogen storage tank on your site and get it filled up periodically by a gas company. These tanks can either be rent (from said gas company) or bought and an evaporator is required for you to be able to use the nitrogen in it. An evaporator transforms the liquid nitrogen into usable nitrogen in gaseous form. Just like nitrogen in bottles, it gets transported to your company by trucks. However, in this case, the nitrogen is transported in a big thermally insulated tank truck. The liquid nitrogen is then pumped from the truck into your insulated storage tank. It is also possible to order liquid nitrogen in smaller cans for smaller consumptions, these small tanks are known as dewars. Also, just like bottled nitrogen, liquid nitrogen is produced by a cryogenic nitrogen plant.

Advantages: Disadvantages:
  • Since the nitrogen you have is readily available, peak flows are allowed.

  • It is, in most cases, more cost effective compared to bottled nitrogen.

  • Small capacity adjustments are relatively easy should your production and nitrogen requirements increase (if your evaporator can handle them without freezing)

     

     

     

     

  • Tank insulation is never perfect. This means the liquid gas will heat up, evaporate in the tank itself and pressure will rise until the safety valve opens and blows part of the gas off. These losses are called boil-off losses.*

  • Long term contracts with the gas company are common practice (typically 5-7 years).

  • Besides the tank you also need special foundation (which can withstand the extreme cold temperatures in case of a leak) and an evaporator.

  • Not environmentally friendly.

  • Safety concerns (liquid nitrogen is -196°C, there is a frostbite risk when working with liquid nitrogen)

  • The evaporator can freeze up when your nitrogen consumption is higher than nominal or when it’s cold outside.

On Site Cryo Production

When your nitrogen consumption is extremely high, a gas company might install a (small) cryogenic nitrogen plant at your production site. This is the same type of nitrogen generator as the one used to create the nitrogen that gets transported in bottles and tank trucks. You can read more about cryogenic nitrogen generators in the article below. (link to article cryo)

Generating your own nitrogen

As opposed to the previous methods of getting nitrogen, generating your own does not involve the cryogenic process. Its extreme temperatures are nowhere to be found in membrane or Pressure Swing Adsorption (PSA) nitrogen generators. These generators have to separate the air into its components in a different way. PSA and membrane are two very different technologies, however they both need a stream of compressed air in order to work.

Because these technologies are so different from cryo, the composition of the resulting gas will be different. Cryogenic nitrogen gas has a fixed, very high purity level. The nitrogen purity of commercially available generators can be adjusted to match your preferences, but gaining the same level of purity as cryo generated nitrogen is extremely inefficient. With these machines, higher purity levels require more power, resulting in higher running costs. That being said, for most applications the purity levels of cryogenic nitrogen are overkill. You can read more about nitrogen purity here.

Advantages: Disadvantages:
  • In a lot of cases, generating your own nitrogen is the solution with the lowest total cost of ownership.
  • Purity can be set according to your needs, the cost goes down together with N2O2 purity.

  • You are independent from any gas suppliers.

  • The gas price is very stable, you are only susceptible to changes in the price of the electricity to run your installation.

  • It is a safe option (no low temperatures or high pressures).

  • There is no waste (no returning of gas to the supplier, no boil-off losses), you produce what you need.

  • Environmentally friendly compared to other options.

  • Special measures have to be taken to allow for peak flows (e.g. buffer tank, high pressure buffer tank, liquid gas buffer).

  • A slight increase in gas consumption, above the nominal capacity of the installation, will have a bigger impact compared to liquid or bottled nitrogen.

  • If the different components in the installation come from different suppliers, it might make communication & service more challenging.

 

 

 

 

 

Take a Closer Look at PSA and Membrane Generators

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