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Introduction to Chemistry of Diesel Fuels
Published in Chunshan Song, Chang S. Hsu, Isao Mochida, Chemistry of Diesel Fuels, 2020
For use as a fuel for vehicles, natural gas has to be compressed to about 20 MPa (200 bar), which increases its density to about 140 g/liter[9]. The pressure vessels in which CNG is contained are heavy and costly. On the other hand, natural gas can be contained in a relatively dense form at relatively low pressures by using a porous adsorbent such as an activated carbon. The surface area of activated carbons can be about 1500 m2/g or higher. In this form the gas is called adsorbed natural gas (ANG). The ANG fuel can be stored in the fuel tank at about 3.5 MPa (35 bar). This method has been developed to the point of commercial applicability[9]. The density of the gaseous fuel stored by adsorption on commercially available carbon materials at 35 bar is equivalent to that of the gas compressed at 100 bar in a pressure vessel[9]. When the activated carbon powders are made into compact discs of about 30 mm thick and stacked in cylindrical containers, much higher adsorption capacity can be achieved.
A comparative assessment of predicting CH4 adsorption on different activated carbons using generalized regression neural network (GRNN), and adaptive network-based fuzzy inference system (ANFIS)
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2019
Hao Yan, Yulan Mou, Xuefeng Xu, Jinfeng Du, Rui Wang, Pengjun Liu
Natural gas (NG) has a considerable advantage over conventional fuels both from an environmental point of view and for its natural abundance. Adsorbed natural gas (ANG) is a technology in which natural gas is adsorbed by a porous adsorbent material at relatively low pressures. Among adsorbents investigated, carbon materials are the most effective in the storage of natural gas at low pressures (Menon and Komarneni 1998; Parkyns 1995). A description of the adsorption of carbon dioxide, methane, and their binary mixtures on activated carbons focuses on some interesting problems of current adsorption research. There is first the aspect of technological applications. Both carbon dioxide and methane have been implicated as greenhouse gases. Critical issues in the commercialization of adsorbed natural gas storage technology not only include the storage capability of the adsorbent but also the facility of use and the cost of manufacturing. Adsorption techniques (membrane and pressure swing methods) together with porous adsorbents, especially carbons, seem promising candidates for these separations. However, it is still very difficult to evaluate activated carbons for a separation because it is difficult to predict their adsorption behavior. What is missing is a suitable model for the internal structure of carbon (Heuchel et al. 1999). Another stimulation for studying the adsorption comes from theoretical interests on supercritical adsorption. As pointed out by Aranovich and Donohue (1996), there are very few papers that contributed to physical adsorption of supercritical gases. The renewable fuels have great economic and environmental appeal and among the various examples, the biogas has become one of the most interesting to the world community through the energy recovery of waste. The use of gaseous fuels in particular natural gas (CH4 >90%) and CH4 from purified biogas (biomethane), has raised challenges involving storage and transportation due to the low volumetric energy density (Esen and Yuksel 2013; Policicchio et al. 2013). The use of activated carbons has been widely investigated (Ning et al. 2012; Shao et al. 2011; Van Der Vaart et al. 2000) due to their large surface area, high micropore volume, suitable pore size distribution, and hydrophobic character (Sircar, Golden, and Rao 1996). Peredo-Mancilla et al. (2018) determine the CH4 and CO2 pure gas adsorption isotherms on different activated carbons experimentally. It was found that the adsorption capacity to be related to the BET surface area and the micropore volume. Meanwhile, the total pore volume and the mesopore volume did not seem to influence the adsorption process.