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.
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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
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
Amur GPP – single-column NRU
Another project currently under construction is the largest natural gas processing plant. Linde is supporting this project with a nitrogen rejection unit. The aim is to reduce the nitrogen fraction of the natural gas to one or two percent, to make the separated liquefied nitrogen available for use in other processes and to capture the tiny quantities of valuable helium present in the gas (well under one percent) so it can be commercialized.
In the first stage of the single-column NRU designed by Linde, the methane and nitrogen (together with the helium fraction) are separated. The helium is then separated from the nitrogen (based on the different boiling points of the other natural gas components). Stage 2 utilizes a coldbox to cryogenically separate the remaining components so efficiently that over 98 percent of the helium present in the natural gas can be used. The captured nitrogen is used in the downstream helium liquefaction process.
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.
Unlike the Amur GPP, 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.