How Nitrogen or Oxygen Purity Affect Their Cost

Depending on how much nitrogen you use, installing a gas generator might be cheaper than purchasing gas from a supplier. Purchased gas is guaranteed to be of a very high and specific purity, but if you don’t need this level of purity, you could significantly reduce your operating costs by installing a generator and a compressor. Plus, purity and quality are not the same thing.

In this guide, we explain how purity affects the price of generating gases, such as nitrogen. We discuss the different technologies used to increase the purity of your gas and which environments they’re best suited to. We’ll also help you decide whether to install your own gas generator or purchase gas from a supplier.

At Anglian Compressors, we’ve been installing compressed air systems and gas generators since 1977 for clients in industries ranging from manufacturing and food packaging to healthcare and pharmaceuticals. Please call us if you want to discuss your gas generation or compressed air needs with an experienced specialist.

Nitrogen and Oxygen: Purity vs. Quality

Before delving into the impact of purity on the production price of a gas such as oxygen or nitrogen, we need to dispel the common myth that gas quality and purity are the same thing.

The purity of a gas refers to its concentration only. For example, if you purchase nitrogen with a purity of 95%, the content of the gas will be made up of 95% nitrogen plus 5% oxygen and other trace gases.

The quality of a gas, on the other hand, refers to any additional contaminants in the gas, such as oil, dust and water.

Whether you purchase or generate gas, its quality will likely comply with the international ISO 8573-1 standard. Some industries, such as food and drinks and pharmaceuticals, may have to comply with even more stringent quality standards.

However, the key takeaway is that a higher purity doesn’t necessarily translate to a higher quality. The application for which you require gas will determine your desired purity level.

Purchased Gas vs. Onsite Gas Generation

In many situations, generating your own nitrogen can be more cost-effective than buying it from industrial gas companies. While onsite gas generation requires an upfront investment, you can make a return on investment through reduced energy costs in as little as six months.

Even if it takes a few years to realise cost savings, now might be a good time to invest in a gas generator with an air compressor, in light of fuel and energy costs.

Factors that Affect the Cost of Purchased Oxygen and Nitrogen

Besides the initial investment of purchasing and installing gas cylinders, factors that affect the price of gas from a supplier can include environmental taxes and delivery charges, not to mention the price per unit of the gas itself. If ordering gas in bulk, you will also need a storage facility that complies with fire and safety regulations.

Purity is rarely a significant cost factor when purchasing gas from a supplier – the cryogenic mass production process offers virtually no wiggle room when it comes to purity outcomes. In other words, when you buy a gas like nitrogen, it’s almost guaranteed to be of a very high purity.

But if the gas you purchase is unnecessarily pure for your application, you could reduce your operating costs by generating your own.

How Nitrogen or Oxygen Purity Affect Their Cost
How Nitrogen or Oxygen Purity Affect Their Cost

What Impacts the Price of Onsite Oxygen and Nitrogen Generation?

The primary factor that impacts the price of onsite gas generation is the technology that the generator uses. Here’s a quick breakdown of the two most common technologies: pressure swing adsorption (PSA) and membrane technology.

Pressure Swing Adsorption (PSA)

This method involves passing compressed air through molecular sieves, resulting in nitrogen purity levels of up to 99.999% and oxygen purity levels of up to 95%.

Membrane Technology

Compressed air is directed through semi-permeable membranes, which results in nitrogen purity levels ranging from 95% to 99.5%.

When it comes to onsite generators, even seemingly minor variations in purity levels, like 99.9% and 99.999%, can have substantial cost implications. Firstly, there are the initial investment costs, such as the purchase of a gas generator, a compressor for feed air, and the necessary air treatment equipment, and storage tanks. Secondly, there are operating costs such as electricity and maintenance.

How Gas Purity Impacts Price

The purer your nitrogen requirements, the bigger the gas generator you’ll need to achieve a given flow rate. Moreover, the larger your generator, the more electricity and compressed air you’ll use and the higher your maintenance costs will be.

For example, a system that generates nitrogen with a purity of 95% might use two cubic feet per minute (SCFM) of compressed air to produce one SCFM of nitrogen. However, a system that generates nitrogen with a purity of 99.999% might use 12 SCFM of compressed air to produce one SCFM of nitrogen.

That means it can take six times the energy to produce nitrogen with a purity of 99.999% instead of 95%, but such a high purity is often unnecessary.

By adjusting gas purity levels to meet specific application needs, companies producing their own gas can reduce their costs in several ways. Namely, purchasing a small generator and compressor could reduce your initial investment costs. This, in turn, could lead to lower operating costs by reducing your energy consumption and carbon footprint.

What Nitrogen Purity Levels Do I Need?

Here are some general nitrogen purity recommendations for different industries (please keep in mind that the following guidelines are for comparison purposes only):

  1. Preventing Hazardous Conditions (Blanketing): Typically, 95-97% purity is suitable for most applications.
  2. Blanketing Edible Vegetable Oils: Aim for approximately 99.9% purity.
  3. Food Packaging: Around 99.5% purity is sufficient for most applications.
  4. Printed Circuit Boards: Required 99.999% purity to ensure a good solder joint.
  5. Heat Treating Metals: Depending on the materials and treatment method, purity can range from 97% to 99.999% (10 PPM of O2).

In many industrial settings, nitrogen generation systems are more powerful or pure than necessary. Suppose clients are unsure of what purity levels are sufficient for their processes. In that case, they’re likely to err on the side of caution and specify a higher nitrogen purity level than necessary, particularly if they believe that purity translates to quality. 

However, by determining what purity levels you require and specifying your gas generator needs accordingly, you can save a significant sum on running costs.

Learn More about Onsite Gas Generation from the Air Compressor Experts

Should I invest in onsite gas generation to reduce the price of nitrogen or oxygen at your industrial facility? Get in touch with our air compressor specialists, and we’ll gladly lend a helping hand.

At Anglian Air Compressors, we’ve been at the forefront of our industry for nearly five decades. Thanks to our expertise, we can help you determine your gas purity level requirements and select the most suitable system for your specific applications. 

Call us today for product information, advice or a no-obligation quote.