Storage of methane at low pressure in activated carbon under different temperature and flow rate of charge conditions

ABSTRACT Methane storage in adsorbed form in activated carbon (ANG - Adsorbed Natural Gas) has attracted attention in recent years by applying reduced pressures when compared to CNG (Compressed Natural Gas) technology and reduced temperatures, and also for representing an important alternative use of biomethane derived from biogas purification in vehicular and stationary systems. This study aimed an evaluation of methane storage in activated carbon under different conditions of temperature and flow rate of charge in a prototype system. Methane was inserted into the prototype system filled with activated vegetable carbon at reduced pressure (10 bar) using factorial design 2². In the desorption of the system, kinetics was raised to identify the best condition to be adopted between the conduction of the storage trials to allow activated carbon reuse. Activated carbon was characterized with N2 physisorption for the determination of textural characteristics, Helium gas pycnometry for quantification of particle density, and scanning electron microscopy for observation of the morphological structure. Under the conditions adopted in this study, an increase was observed in activated carbon adsorption capacity with decreasing temperature and flow rate during the evaluated range. With this study, it was possible to increase a cylinder storage capacity in approximately 3 times (34,56 V V-1) compared to the hollow cylinder (13,14 V V-1), proving the effectiveness of the adsorbent and the set of variables adopted. In addition, the kinetic study of methane desorption resulted in the adoption of 60 ºC for 30 min for the complete methane delivery.

摘要： 吸附态甲烷存储于活性炭中的技术（吸附天然气，Adsorbed Natural Gas，ANG）近年来受到广泛关注，相较于压缩天然气（Compressed Natural Gas，CNG）技术，该技术可在更低压力与温度条件下实现甲烷存储，同时也是沼气提纯所得生物甲烷用于车用及固定式系统的重要替代方案。本研究旨在评估不同温度与充入流速条件下，活性炭对甲烷的吸附存储性能，实验采用原型系统开展。本研究采用2²因子设计，在10 bar的低压环境下，将甲烷注入装填植物基活性炭的原型系统中。为确定存储实验开展过程中的最优工况以实现活性炭的重复利用，本研究开展了系统解吸动力学实验。通过氮气物理吸附表征活性炭的织构特性、氦气比重瓶法测定其颗粒密度，以及扫描电子显微镜观测其形貌结构。在本研究采用的实验条件范围内，随着温度降低与充入流速减小，活性炭的甲烷吸附容量显著提升。本研究可使储气瓶的储气量较空储气瓶（13.14 V·V⁻¹）提升约3倍（34.56 V·V⁻¹），验证了该吸附剂及所选变量组合的有效性。此外，通过甲烷解吸动力学研究，确定了60℃保温30 min即可实现甲烷完全脱附。