Sequestering Carbon Dioxide in Coalbeds

Abstract

The authors' long-term goal is to develop accurate prediction methods for describing the adsorption behavior of gas mixtures on solid adsorbents over complete ranges of temperature, pressure, and adsorbent types. The originally-stated, major objectives of the current project are to• measure the adsorption behavior of pure CO 2 , methane, nitrogen, and their binary and ternary mixtures on several selected coals having different properties at temperatures and pressures applicable to the particular coals being studied, • generalize the adsorption results in terms of appropriate properties of the coals to facilitate estimation of adsorption behavior for coals other than those studied experimentally, • delineate the sensitivity of the competitive adsorption of CO 2 , methane, and nitrogen to the specific characteristics of the coal on which they are adsorbed; establish the major differences (if any) in the nature of this competitive adsorption on different coals, and • test and/or develop theoretically-based mathematical models to represent accurately the adsorption behavior of mixtures of the type for which measurements are made.As this project developed, an important additional objective was added to the above original list. Namely, we were encouraged to interact with industry and/or governmental agencies to utilize our expertise to advance the state of the art in coalbed adsorption science and technology. As a result of this additional objective, we participated with the Department of Energy and industry in the measurement and analysis of adsorption behavior as part of two distinct investigations. These include (a) Advanced Resources International (ARI) DOE Project DE-FC26-00NT40924, "Adsorption of Pure Methane, Nitrogen, and Carbon Dioxide and Their Mixtures on W et Tiffany Coal", and (b) the DOE-NETL Project, "Round Robin: CO 2 Adsorption on Selected Coals". These activities, contributing directly to the DOE projects listed above, also provided direct synergism with the original goals of our work.Specific accomplishments of this project are summarized below in three broad categories: experimentation, model development, and coal characterization. Experimental Work:Pure-gas adsorption measurements were conducted for methane, nitrogen, ethane, and carbon dioxide on ten solid matrices: wet Fruitland coal (OSU #1 and OSU #2), wet Lower Basin Fruitland coal (OSU #3), wet / dry Illinois #6 coal, wet Tiffany coal, dry Beulah Zap coal, dry Wyodak coal, dry Upper Freeport coal, dry Pocahontas coal, and dry activated carbon.Binary and ternary adsorption measurements were conducted for mixtures of methane, nitrogen and CO 2 at a series of compositions on four different matrices: Fruitland coal, Illinois #6 coal, Tiffany coal, and activated carbon. Ternary measurements were also measured for methane/nitrogen/CO 2 mixtures on wet, mixed Tiffany coal and on dry activated carbon.The expected experimental uncertainty of the pure-gas adsorption data is on average about 3%. However, the expected uncertainties in the amoun...