Adsorbed natural gas (ANG) technology is a promising alternative to traditional compressed (CNG) and liquefied (LNG) natural gas systems. Nevertheless, the energy efficiency and storage capacity of an ANG system strongly depends on the thermal management of its inner volume because of significant heat effects occurring during adsorption/desorption processes. In the present work, a prototype of a circulating charging system for an ANG storage tank filled with a monolithic nanoporous carbon adsorbent was studied experimentally under isobaric conditions (0.5–3.5 MPa) at a constant volumetric flow rate (8–18 m³/h) or flow mode (Reynolds number at the adsorber inlet from 100,000 to 220,000). The study of the thermal state of the monolithic adsorbent layer and internal heat exchange processes during the circulating charging of an adsorbed natural gas storage system was carried out. The correlation between the gas flow mode, the dynamic gas flow temperature, and the heat transfer coefficient between the gas and adsorbent was determined. A one-dimensional mathematical model of the circulating low-temperature charging process was developed, the results of which correspond to the experimental measurements.

The present work focused on the experimental study of the performance of a scaled system of adsorbed natural gas (ANG) storage and transportation based on carbon adsorbents. For this purpose, three different samples of activated carbons (AC) were prepared by varying the size of coconut shell char granules and steam activation conditions. The parameters of their porous structure, morphology, and chemical composition were determined from the nitrogen adsorption at 77 K, X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), and scanning electron microscopy (SEM) measurements. The methane adsorption data measured within the temperature range from 178 to 360 K and at pressures up to 25 MPa enabled us to identify the most efficient adsorbent among the studied materials: AC-90S. The differential heats of methane adsorption on AC-90S were determined in order to simulate the gas charge/discharge processes in the ANG system using a mathematical model with consideration for thermal effects. The results of simulating the charge/discharge processes under two different conditions of heat exchange are consistent with the experimentally determined temperature distribution over a scaled ANG storage tank filled with the compacted AC-90S adsorbent and equipped with temperature sensors and heat-exchanger devices. The amounts of methane delivered from the ANG storage system employing AC-90S as an adsorbent differ from the model predictions by 4–6%. Both the experiments and mathematical modeling showed that the thermal regulation of the ANG storage tank ensured the higher rates of charge/discharge processes compared to the thermal insulation.

Physicochemical regularities are studied for the synthesis of molded active carbons based on coconut shells and peat, with a latex emulsion and a carboxymethyl cellulose (CMC) sodium salt solution being used as binding agents. The materials are obtained at compacting pressures of 25, 50, and 100 MPa. The specific surface areas of the composite samples obtained from peat and coconut shells are S_BET ≈ 1320 and ≈1290 m²/g, respectively. The specific micropore volumes of the composites based on peat and coconut shells are W₀ = 0.50 and 0.45 cm³/g, respectively. Latex-modified carbon samples have a higher bulk density than those molded with CMC. The molding of the active carbons is accompanied by partial degradation of their porous structure. The Dubinin theory of volume filling of micropores (TVFM) has been employed to calculate the values of adsorption and active specific capacity of the molded adsorbents with respect to methane at a temperature of 273 K and a pressure of up to 100 bar. The experimental and calculated data have shown that the active capacity of the new microporous carbon composite materials may be as large as 180 m³ (NTP)/m³, when the pressure drops from 100 to 1 bar. It has been concluded that it is reasonable to employ the TVFM for preliminary calculations of the parameters of adsorption systems used for natural gas storage.