Chemistry:Adsorbed natural gas

Natural gas burns cleanly as a fuel, making it useful in many vehicles and applications such as cooking, heating or running generators. It contains mostly methane and ethane. These light gases have very high vapor pressure at ambient temperatures, and their storage requires either high-pressure compression, adsorbent systems or an extreme reduction of temperature.

Recently, a process has been introduced to store natural gas called adsorbed natural gas (ANG). In this process, natural gas adsorbs to a porous adsorbent at relatively low pressure (100 to 900 psi) and ambient temperature, solving both the high-pressure and low-temperature problems. If a suitable adsorbent is used, it is possible to store more gas in an adsorbent-filled vessel than in an empty vessel at the same pressure. The amount of adsorbed gas depends on pressure, temperature and adsorbent type. Since this adsorption process is exothermic, an increase or decrease of pressure or an increase or decrease of temperature enhances the efficiency of the adsorption and desorption process. Activated carbon is an adsorbent with high surface area that can be used in ANG storage tanks. Currently, researchers are developing new adsorbents with higher adsorption ratio to optimize this process.

ANG technology companies, such as Cenergy Solutions, Inc. (www.cenergysolutions.com), Adsorbed Natural Gas Products (ANGP) (www.angpinc.com), Ingevity Corporation (NYSE: NGVT) (www.ingevity.com), has deployed commercially viable ANG tank technology in the USA for CNG vehicles and bio-methane facility storage. Cenergy Solutions received a US patent on July 10, 2018 that helps the adsorption, desorption and filtering of the adsorbents so they do not escape from the cylinder or tank. Cenergy Solutions was also awarded the Clean Cities, Clean Air Champion Award for 2017 and ANGP was awarded the 2016 Frost & Sullivan New Product Innovation Award for Gas Storage for Natural Gas Vehicles for their work in commercializing ANG technology. In March 2016, ANGP's Generation 1 ANG storage system proved to be the first NGV2 compliant ANG storage system available to the market. The system has been demonstrated on a 2014 Ford F150, with an engine system capable of low-pressure natural gas operation. Cenergy Solutions introduced the first conformable ANG tank on a 2016 Ford F150 in May 2016 with their low pressure EPA approved bi-fuel conversion system. Validation ANG tank prototypes have been operational on an 8.1-liter Chevrolet Suburban; and the first ANG system to be used commercially was delivered in December 2015 on an OEM dedicated Dodge Ram 2500 with a 5.3-liter engine and has been in commercial operation since.

ANG technology is a significant step toward solving the “chicken and egg” challenge for broad and rapid adoption of CNG. The ANG system creates the low pressure, conformable CNG storage solution for full-scale, affordable NGV-hybrid deployment in the US. Moreover, the lower compression pressures required to “fill” ANG tanks also allows for the more rapid growth of a ubiquitous CNG refueling network. Cenergy Solutions, Inc. introduced the first low pressure ANG compressor that is CSA and UL certified to be used as a natural gas appliance. This compressor will solve the natural gas fueling infrastructure problem. Due to the significantly lower capital investment associated with lower compression requirements, CNG infrastructure will be more easily and cost-effectively added to the network of gas stations and truck stop.

ANG technology also creates a market for compact, affordable, low-pressure CNG Home Refueling Appliances (HRA’s) that will allow consumers to fill their vehicles at home connecting directly to their utility gas line. Cenergy Solutions has introduced this home and business compressor to the US, Canadian and Mexican market.

Ford Motor Company’s Fleet Sustainability and Technology Manager is quoted as saying, “The highest cost of a CNG filling station is the compressor, because compressing to 3,600 psi takes a tremendous amount of energy. By reducing that compression to 1,000 psi, or even further to the “Holy Grail” of 500 psi, this is game-changing technology because it enables home refueling, and you have 53 million potential fill points at every residence in the country that has natural gas running into it.”

ANG is also being tested for other methane storage applications, including CNG fueling station storage, virtual pipelines, and fugitive/ wellhead methane capture systems. Other significant opportunities for ANG include home heating and cooking applications in developing countries and in Southeast Asia.

References

7. http://www.angpinc.com