General equations for calculation of the capacity and thermodynamic properties of adsorption methane storage systems were written. Experimental results for methane adsorption on AU-1 adsorbent were analyzed and plotted in the nomograph of capacity and thermodynamic properties of the adsorbentadsorbate-gas adsorption system. Methods for graphical calculation of the processes occurring in the system were presented.Adsorption storage systems for natural gas (methane) are very promising not only for storage but also for transportation. An adsorption storage system comprises a container fi lled with a microporous adsorbent. A gas volume of 150-193 m 3 per m 3 of the best carbon adsorbents, e.g., carbon fi ber [1] and active carbons [2], and, according to calculations, 230-284 m 3 per m 3 of metal-organic adsorbents [3], is achieved at pressures of 3.5-7.0 MPa. This is comparable to the corresponding values for compressed natural gas at 20 MPa. Industrial adsorbents (active carbons and zeolites) were developed for different problems so that their capacity is usually lower at 90-110 m 3 /m 3 at 3.5 MPa and 20-25°C.Adsorption storage systems are considered to be safer than traditional compressed and liquid storage systems because the stored gas is bound, which prevents detonation within a tank and rapid loss of gas through a breach. Highly hazardous acetylene is commonly stored in active-carbon adsorption storage systems [4]. An adsorption storage system can conserve energy because of the lower loading pressure and other features.The high heat of adsorption of methane is the principal drawback of natural-gas adsorption storage systems. Considering the signifi cant amount of stored gas, the temperature changes considerably during adsorption and desorption. The adsorbent temperature during loading increases by 30-60 K [5] although the adsorbent dynamic capacity decreases as a result [6]. The reverse effects arise during desorption, i.e., the temperature decreases whereas the adsorption capacity and the amount of residual gas in the empty tank increase. The heat of desorption has a smaller negative effect because of the low residual gas pressures [7].Methods for dissipating heat of adsorption (during loading) or adding heat (during gas release) were developed because the thermal effects were signifi cant. They usually involved placing a heat exchanger within the adsorbent or purging with natural gas.The majority of the research was either experimental or simulated by computer. Both approaches were expensive or labor-intensive and poorly suited for practical calculations of the many processes occurring in adsorption storage systems. Graphs of the properties of various compounds are convenient to use in practice to calculate the processes occurring in them.

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.

No abstract

No abstract