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Thermal effects of adsorption and desorption, leading to temperature fluctuations and losses of adsorption storage systems capacity in the processes of gas charging and discharging, are the main obstacle to the wide practical application of adsorbed natural gas (ANG) technology. This work presents a numerical simulation of heat and mass transfer processes under various cyclic operation modes of a full-scale adsorption storage tank with various thermal control systems. The high-density monolithic adsorbent KS-HAM, obtained on the basis of industrial activated carbon KS-HA, was used as the adsorption material. The phase composition, surface morphology, and porous structure of the sorbents were studied. The adsorption of methane on the KS-HA adsorbent was measured. It is shown that increasing the duration of charging leads to obtaining additional capacity of the ANG system; however, the final efficiency and benefit at the end of the charging–discharging cycle are determined by the efficiency of the thermal control system and the gas-discharging mode. It has been shown that the presence of a finned thermal control system allows for charging the adsorption storage tank 3–8 times faster and provides an 8–24% greater amount of gas discharged at the discharging stage compared to the ANG system without fins. [ABSTRACT FROM AUTHOR]

One-stage synthesis technology for preparing carbon adsorbents with tailored porosity from agricultural waste is worthwhile due to their extensive application value. Thermal gravimetric analysis, low-temperature N2 adsorption, X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), and Raman spectroscopy were used to record the structure transformations of carbon materials, namely pore development, proceeding in the course of the step-wise pyrolysis of renewable and low-cost raw materials such as walnut shells (WNSs), which was carried out within a temperature range of 240–950 °C in a CO2 flow. The minimum threshold carbonization temperature for preparing nanoporous carbon materials from WNSs, determined by the examination of the N2 adsorption data, was 500 °C. The maximum specific micropore volume and BET surface achieved in the process without holding a material at a specified temperature were only 0.19 cm3/g and 440 m2/g, respectively. The pyrolysis at 400–600 °C produced amorphous sp2 carbon. At a temperature as high as 750 °C, an increase in the X-ray reflection intensity indicated the ordering of graphite-like crystallites. At high burn-off degrees, the size of coherently scattering domains becomes smaller, and an increased background in X-ray patterns indicates the destruction of cellulose nanofibrils, the disordering of graphene stacks, and an increase in the amount of disordered carbon. At this stage, pores develop in the crystallites. They are tentatively assigned to crystallites with sizes of 15–20 nm and to micropores. According to the Raman spectra combined with the XRD and SAXS data, the structure of all the pyrolysis products is influenced by the complex structure of the walnut shell precursor, which comprises cellulose nanofibrils embedded in lignin. This structure was preserved in the initial stage of pyrolysis, and the graphitization of cellulose fibrils and lignin proceeds at different rates. Most of the pores accessible for gas molecules in the resulting carbon materials are associated with former cellulose fibrils. [ABSTRACT FROM AUTHOR]

Capture and storage of LNG vapors in the adsorbed state is envisioned as an effective way to improve the LNG terminal performance. A synthetic carbon xerogel was proposed as a promising adsorbent for methane vapors in the LNG terminal combined with an adsorbed natural gas (ANG) module. The textural properties of the adsorbent were investigated by X-ray diffraction, scanning electron microscopy, and low-temperature nitrogen adsorption. An approach based on the theories of volume filling of micropores, a monolayer capacity on the mesopore surface, and the capillary condensation in the mesopores was applied to the experimental data on methane adsorption to evaluate the adsorption capacity of the adsorbent over the sub- and supercritical P,T-ranges. It was found that the capillary condensation of methane in mesopores ensured an extraordinary adsorption capacity of the adsorbent, achieving 540 m3(NTP)·m−3 at the boiling point. The adsorption- and temperature-induced deformation of the adsorbent, and the thermal effects arising during adsorption were examined with a view of the performance of the LNG terminal combined with the adsorber for capturing and accumulating LNG vapors. The ANG tank loaded with the carbon xerogel ensured the maximum amount of gas supplied to the consumer at temperatures close to 140 K. A comparison of the adsorption performances of the carbon xerogel and a commercial activated carbon characterized by a wider pore size distribution made it possible to identify a difference in the optimal operational conditions of their application for the LNG–ANG technology. [ABSTRACT FROM AUTHOR]