On Site Generation

On-site gas production plants provide custom solutions for the exact purity, pressure, and flow requirements of the customer. Typically it’s a dedicated, uninterrupted supply of hydrogen, oxygen, nitrogen, generated directly at your site.

Systems can accommodate small volumes, similar to bulk liquid supply up to large-scale requirements such as Air Separation Units and from low to high purity needs, can be supplied within on-site plants. Generation systems are available in a wide array of standard and customised generators adapted to meet the needs of the site, they rely on cryogenic, adsorption, and membrane technologies to deliver the levels of gas flow and purity required.

Nitrogen & Oxygen On-Sites

Nitrogen and Oxygen generation plants cover adsorption (PSA / Membranes) and the larger cryogenic plants.

• How Cryogenic plants work

An air separation plant separates atmospheric air into its primary components, typically nitrogen and oxygen. The most common method for air separation is fractional distillation.

Pure gases can be separated from air by first cooling it until it liquefies, then selectively distilling the components at their various boiling temperatures. The process can produce high purity gases but is energy-intensive.

This is the most common process used by the large suppliers where these plants are located next to a large user of a particular gas e.g. Oxygen and the other gases are then sold off in bulk liquids to other customers.

• How PSA Generators work

Ad-sorption is the physical process of separating molecules. Pressure Swing Adsorption (PSA) generators generate oxygen or Nitrogen by separating it from the air. Air is 21% oxygen and 78% nitrogen, and 1% other gases mainly argon.

PSA generators, has a vessel containing a molecular sieve which is filled with compressed air. The nitrogen or oxygen molecules are adsorbed by the sieve material while the desired gas N2 or O2 molecules drift past and are collected in a receiver tank. Pressure is then released from the vessel, and the undesired gas molecules are vented to the atmosphere. While the depressurization is occurring, the cycle is repeated in a second vessel. The process is repeated swinging from one vessel to another to reach purity levels and demand required. The molecular sieve is different depending on what gas you require.

• How Nitrogen Membrane Generators Works

Pressurized air is fed to one end of hollow fibre membranes. Membranes contain a bundle of hollow fibres with holes small enough to allow the smaller oxygen molecules to exit through them under pressure. The permeation rates of water vapor, CO2, and oxygen contained in the air stream are faster than nitrogen and argon and will rapidly diffuse through the fibre walls.

The slower diffused nitrogen molecules remain in the fibre bore and are collected as the nitrogen product gas. The air flow rate will determine how much undiffused oxygen remains with the nitrogen gas. The nitrogen product gas is extremely dry, with atmospheric dew points typically below -40°F. The membranes act like a filter with no moving parts and continuously generate nitrogen at selected flow and purity.

Hydrogen On-Sites

Hydrogen can be generated on-site in one of three different ways – electrolysis, steam methane reforming and methanol cracking.

• Electrolysis involves the splitting of water into hydrogen and oxygen by the application of electrical energy.
• Steam methane reforming involves the reforming of natural gas through the use of steam and a catalyst to produce hydrogen and carbon dioxide.
• Methanol cracking involves the cracking of methanol into hydrogen and CO2/CO

Things to consider:

• If you are buying outright these systems will impact your cash flow, some companies will offer this to you in return for a facility fee / rental. Be warned the prices will only go up!
• They have a limited lifespan and warranties – unless you’re going BIG and require lots of maintenance to keep them working to their optimum levels. If your renting, then this will not be an issue – you end up paying for it through your facility charge.
• Over spec the system! Several suppliers will offer you systems that meets your average gas usage requirements as to ensure initial costs are kept low. However, as your business grows and you require more gas – putting extra loads on the generator the purity of gas falls and you have more breakdowns. This incurs costly shutdowns as you do not have a backup whilst the generator is getting repaired which you most likely will have to pay.
• Generation is not cost free – there is no such thing as free gas. You will incur higher electricity costs in order to generate the gas required. Once way around this is by using solar/wind which again costs to install.