Experimental study of the ANG storage tank during charge and discharge

Comparative experiments were carried out to develop an adsorbed natural gas (ANG) storage tank for replacing a domestically used liquefied petroleum gas (LPG) tank. Coconut shell activated carbon SAC-02 with S_BET of 2 074 m²/g was selected as an adsorbent. A cylindrical steel pressure vessel, which was respectively equipped with a helical heat exchanging pipe, a U-shaped pipe and a perforated tube, was used to evaluate the effect of the cooling/heating water and the charge/discharge patterns on temperature fluctuation of the adsorbent bed and the charged/discharged amount of the storage tank. Tests were undertaken at ambient temperature, under pressure of 3.5 MPa and the flow rate 15 L/min of the natural gas. It shows that, about 10℃ fluctuation of temperature at the central region of the storage tank has been cut down by circulating the cooling/heating water along the helical pipe instead of the U-shaped pipe, and the total charged/discharged amount of the gas from the vessel has also correspondingly increased by about 18% and 14%, respectively. Charging/discharging the gas through the perforated tube can reduce the temperature fluctuation amplitude about 15℃ and 10℃, respectively, but the total amount of gas charging/discharging from the vessel has been decreased by 2% and 7%. It suggests that the running water at ambient temperature is an effective medium for managing the thermal effect of a domestically used ANG vessel in the charge/discharge process, and conformable design of the vessel should be undertaken by optimization among the measures of introducing supplemental heat, heat and mass transfer enhancement of the adsorbent as well as the charge/discharge methods.