In-House Nitrogen Generation: A Time & Money Saving Endeavor

NITROGEN IS THE SECOND MOST WIDELY USED GAS IN INDUSTRY

Tasteless, odorless, inert, and non-combustible, nitrogen is an important element used for a variety of different industrial purposes.

 

Used in many different industries for a variety of purposes, nitrogen is most commonly used in the industrial process as a gas.

• Food and Beverage: Modifying atmosphere packaging (MAP) to increase shelf life.

• Chemicals: Tank blanketing.

• Laser cutting and Metal Formation: Prevention of oxidation.

• Plastics: Gas assist injection molding, preventing carburization and combustion.

• Oil, Gas, and Mining: Reduces risk of combustion.

• Electronics: Eliminates dross.

For these uses and others, nitrogen is most often purchased in bulk liquid supply. This is the old-fashioned way that many are accustomed to, but it comes with a heavy (sometimes sneaky) ongoing cost.

Keep reading to learn how switching to Pressure Swing Adsorption (PSA) for nitrogen generation in-house can save you 50 – 90% over bulk liquid supply.

 

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Purchasing Bulk Liquid Supplies

Cryogenic Separation Method

Before we get into the savings opportunities through in-house nitrogen generation, we first must understand how bulk liquid suppliers generate nitrogen through cryogenic separation. In this process, argon, oxygen, and nitrogen are separated as each component reaches its boiling point temperature:

• Argon 297° F

• Oxygen 303° F

• Nitrogen 320° F

A phase change occurs from the gas phase to the liquid phase. Fractional distillation is the process to separate and collect argon, oxygen, and nitrogen.

 

Costs & Specs

Once collected, nitrogen is an incredible asset that can be packaged and sold for industrial use. Nitrogen is priced in 100 cubic foot increments (CCF), which means one gallon of liquid nitrogen is 93.11 cubic feet of nitrogen gas. The rates you will pay for this nitrogen vary not only by the vendor, but by the region, and generally ranges from $0.40 to $1.00 or more per CCF.

But CCF is only one aspect of what you’re ultimately paying for when you buy from bulk liquid suppliers. Built into your contract or CCF fees, you’re also paying for:

• Tank Rental: Often $2,000 or more per month.

• Delivery Charges: As much or more than $100 per delivery.

• Environmental Surcharges: $35 to $50 per delivery.

• Telemetry Charge: To measure usage $75 to $100 per month.

• Taxes & tank inspection fees.

These charges are added to the fees incurred, raising the price to $1.15 to $2.00 or more per CCF. To make matters worse, 10 to 15% of the nitrogen gas evaporates and is vented into the atmosphere because its temperature rises above 321° F.

This is, literally, your money being vented into thin air.

 

Contracts & Storage

To compound the usage fees, both fixed and variable substantial costs are involved to prepare your facility to accept liquid nitrogen storage.

Bulk liquid nitrogen contracts are designed specifically to protect the supplier—not you. Complicated and evergreen, most require 12 months’ notice of cancellation to take effect. This is usually overlooked and noticed when it is too late to modify.

Key needs for onsite bulk nitrogen storage:

• A concrete pad with fencing and signage for onsite storage.
• Safety measures, proper training of personnel, and safety gear.
• Ventilation and air monitoring.
• Regular refilling space and time consumption.
• Emergency preparedness in the case of leaks or spills with containment apparatus.
• Insurance costs for protection against accidents or liabilities.
• Irregular delivery and replenishment where you are at the mercy of the supplier.

Now, let's take a look at the alternative approach.

 

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Generate Nitrogen With Pressure Swing Adsorption

With pressure swing adsorption technology, companies can generate their own nitrogen from compressed air—for a fraction of the cost. Taking advantage of 78% N₂ in the ambient air, you too can benefit from Pressure Swing Adsorption (PSA) to reduce the cost of Nitrogen by 50 to 90% over bulk liquid nitrogen.

 

How Does Pressure Swing Adsorption Work?

Let’s get technical.

PSA is a separation technology that uses compressed air to separate oxygen, argon, and other trace elements to produce nitrogen from 95% to 99.999% purity. The nitrogen is separated in a gaseous state and stays in a gaseous state.

A nitrogen generator consisting of twin towers is fed compressed air through an activated Carbon mist eliminating filter, which purifies the air before it enters the pressure tanks. Each tower is filled with Carbon Molecular Sieve Media (CMS) that is porous and adsorbs the oxygen molecule when pressurized and will not accept the nitrogen molecule which is slightly larger.

The compressed air enters tower 1 and the tower begins to pressurize, and the oxygen molecule is adsorbed by the CMS. During this period under pressure, the oxygen molecule is held in the media and the nitrogen molecule is released to the process. All while remaining in a gaseous state. After a programmed time, the first tower is rapidly de-pressurized allowing the oxygen to be released from the CMS media and vented into the air. While Tower 1 is de-pressurizing, Tower 2 is building pressure undergoing the same process of creating nitrogen.

This switching repeats every 60 seconds providing a constant monitored flow of nitrogen to the process in the facility.

The CMS material is porous, however, the oxygen molecule under pressure adheres within the pore of the CMS The nitrogen molecule will not adhere to the CMS. During the de-pressurization of the tower the tower is automatically closed to the nitrogen feed process and the oxygen is desorbed from the CMS.

Note: Electronic monitoring allows the switching of the towers and sequentially closes and opens tower valves so that oxygen is not released into the nitrogen feed process downstream. A flow meter and oxygen analyzer closely monitor the nitrogen after the process.

 

 

Nitrogen Purity

Why is nitrogen purity important? Nitrogen purity is based on its relationship to oxygen. The term “purity” often gets confused with “cleanliness” or “medical grade.” When considering the equation for switching to in-house nitrogen generation, understanding your purity level, and generating only what you need, will play directly into your cost savings.

Let’s break it down.

Very simply, 99.999% nitrogen purity is 10 parts per million (PPM) oxygen—the highest purity level available. Bulk liquid nitrogen is by default (10PPM) oxygen. You have no choice but to use the highest purity nitrogen and of course pay for that purity too. However, only very few applications require that level of purity. 

As you can see on the chart below, the higher the purity the greater the requirement for compressed air volume:

 

 

Having the nitrogen purity (relative to oxygen content) correct will determine energy savings. When generating nitrogen in-house, compressed air is most of the cost of that nitrogen generation. The higher the purity, the harder the compressor must work, the more electricity is used to operate the compressor.

As seen below, the top ten uses for nitrogen in the United States and the normal nitrogen purities that they require, most operations can operate at 95% purity, creating a cost savings opportunity for you.

 

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In House Nitrogen Generation Saves 50 To 90%

Worldwide, nitrogen users are looking for more reliable and more cost-effective means to obtain the nitrogen they need to serve their process.

Companies are now beginning to see the benefits of an in-house nitrogen generation system. This comes from a variety of triggering factors like the reliability of the nitrogen supply, the sharp rise in the cost of nitrogen, and a closer observation of the purities needed. Companies are looking toward PSA technology to be a stable, mature technology that produces savings of 50 to 90% over bulk liquids N₂.

Diversified Air Systems (DAS), a Motion & Control Enterprises (MCE) company, are experts in nitrogen generation and have consulted hundreds of customers through PSA applications at their operation.

 

One customer saved $500,000+ over bulk liquid supply in 18-months, and fully paid back their nitrogen generation investment in 26-18 months.

 

Other customers have grown accustomed to additional benefits like:

1. Nitrogen Independence. No more excessive bills or shortages.

2. The ability to control their own purity level and pay only for what they truly need.

3. Superior results and the ability to reduce operating expenses generating more profitability.

 

Are you considering an N₂ generator and the cost saving benefits that in-house nitrogen generation can produce for you? Reach out to one of our experts today!