A new carbon adsorbent will enhance the efficiency of liquefied natural gas storage.

It is well known that when handling liquefied natural gas (at a temperature of minus 161 degrees), the formation of vapor gas is inevitable during its storage and transportation. For both environmental and economic reasons, the release of vapor gas into the atmosphere or its flaring is undesirable. Traditionally, compressors are used to return the vapors to the liquefaction cycle or to direct them as fuel to energy installations, including for internal use. However, these approaches are not always applicable.

For instance, in storage systems for liquefied natural gas intended for small consumers, a vapor recovery module is not always provided. Since their gas consumption levels often fluctuate, methane vapors can pose problems and lead to negative consequences. Therefore, it is essential to develop modern and effective solutions for vapor utilization.

Recently, the technology of adsorptive accumulation of natural gas has gained significant importance, which involves using a special porous sorbent in the storage system. This technology is being developed as a more energy-efficient and fire- and explosion-safe alternative to storing gas in compressed form, as it allows for the accumulation of a comparable or greater amount of gas at much lower pressures (3.5-7 MPa) compared to compressed gas.

For liquefied gas, the adsorptive technology may not serve as an alternative but rather as a complement to the existing infrastructure. Adding an adsorptive module not only captures the released gas but also enhances safety. It is important to note that the adsorptive technology can be particularly effective at subcritical temperatures (below minus 83 degrees). The presence of mesopores (ranging from two to 50 nanometers in width) in the material structure significantly increases its adsorption capacity under cryogenic conditions. At these temperatures, capillary condensation occurs in the mesopores, where the density of the adsorbed gas reaches that of the liquid phase. Therefore, such a sorbent can store much more methane.

To produce the new adsorbent, researchers utilized wood waste. Initially, the raw material was carbonized (burned to charcoal), and then the charcoal underwent a two-stage activation process. In the first stage, a large number of micropores were created, which were then transformed into mesopores during the second stage of activation. After activation, the finished adsorbent was molded into monolithic blocks. The manufactured blocks successfully passed tests as part of a prototype accumulator, confirming the adsorbent's effectiveness in capturing evaporated methane. In addition to the adsorbent itself, the authors proposed a conceptual technological scheme for accumulating vapor gas.

“We propose a synergistic solution where the adsorptive technology becomes part of the infrastructure for storing and transporting liquefied natural gas, enhancing its reliability, efficiency, and safety,” said one of the authors, Alexander Grinchenko, a graduate student at the Laboratory of Sorption Processes at the Institute of Physical Chemistry and Electrochemistry of the Russian Academy of Sciences.

Natural gas is the only type of fossil fuel whose consumption is expected to grow in the future rather than decline. This is due to its relative affordability and significantly lower emissions of harmful substances during consumption compared to coal and oil. The "Strategy for the Scientific and Technological Development of the Russian Federation" identifies priorities such as transitioning to environmentally friendly and resource-saving energy and improving the efficiency of hydrocarbon extraction and deep processing. New modern technologies for the extraction and energy sectors meet these objectives and are highly relevant.

The research was conducted with financial support from the Russian Science Foundation.