Nitrogen Rejection Units (NRUs)

Tailored process technologies complemented by modular builds to meet all performance, efficiency and cost targets.

Removing Nitrogen to Increase Thermal Efficiency

Demand for natural gas is growing. It is viewed as an increasingly important stepping stone on the journey towards a low-carbon economy. When extracted, natural gas is a mixture of gases, with hydrocarbons being the main component. However, raw natural gas also frequently contains the inert gas nitrogen. Nitrogen lowers the heating value of natural gas and increases transport volumes.  The challenge lies in reducing this nitrogen content to typically 3-4 percent for pipeline specifications or even 1 percent for storage as liquefied natural gas (LNG). Linde offers a range of nitrogen rejection units (NRUs) for the safe and economical separation of nitrogen. These NRUs lower the nitrogen content in natural gas to pipeline specifications or to below one percent for storage. This reduces both transport volumes and increases the calorific value of the gas, thus meeting the high requirements of industry and trade.

Nitrogen rejection units

Perfect Fit for Individual Needs

Our portfolio for rejecting nitrogen from natural gas includes single-column, single partitioned column and double-column processes as well as double-column processes with an enrichment step. Various modular designs combine the highest quality levels with accelerated delivery schedules. Our modular NRUs comprise a process module, a coldbox and two pump modules.

Reaching beyond our modular portfolio, we also offer customized configurations tailored to the individual composition of the gas in relation to both the nitrogen content and other impurities, which could solidify in the cryogenic process. In addition, we engineer hybrid processes to recover other fractions of interest. If helium is present in the gas stream in relevant quantities, for example, we combine nitrogen rejection with helium recovery. High-purity helium can be obtained through a hybrid configuration where pressure swing adsorption (PSA) is followed by our HISELECT® gas purification units specially engineered to offer excellent energy efficiency, selectivity and robustnes.

NRU coldbox

NRU Highlights

  • Over 130 years of experience in the fabrication of cryogenic modules and packaged equipment
  • Core fabrication facilities in Germany complemented by satellite workshops worldwide for optimized logistics
  • Proprietary technologies designed to the highest quality standards
  • Perfect fit for individual needs with multiple process options and designs tailored to individual needs
  • Modular designs bundling process module, coldbox and two pump modules for time, cost and quality gains
  • Full project lifecycle - from process consulting to turnkey handover
Nitrogen rejection unit (NRU) Karratha, Australia

Australia - Double-Column NRU

Moving over to the other side of the world, a double-column design proved to be the best choice for one of Australia’s largest natural gas processing plants, which is also currently under construction. Linde’s role was to develop an NRU to improve the calorific value of the low-quality gas by reducing the nitrogen fraction. In other words, upgrade the natural gas so it can be fed into the local gas network.

The minimal helium fractions present in the comparatively low-grade Australian natural gas are not economically viable. So it makes sense to remove the intrinsically worthless nitrogen and release it to the atmosphere. A double-column process emerged as the most energy-efficient solution. Highly pressurized liquid nitrogen can be drawn from the lower of the two superimposed cryogenic columns to provide a refrigerant for the process. The nitrogen is fed to the upper column, where it expands and thereby cools from around minus 150 degrees Celsius to minus 180 degrees Celsius.

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