J. Rodney Diehl

Triboelectrostatic separation of fly ash and charge reversal

Triboelectrostatic separation has been investigated as a method for separating unburned carbon from coal combustion fly ash. It was found that when a fly ash is exposed to moisture before it undergoes separation, the charging properties of the components of the fly ash change significantly. The mineral and carbon components of the fly ash appear to charge oppositely to how they were charged before exposure to moisture. A correlation was found between the degree of charge reversal and the relative amounts of leachable ions, especially calcium and sodium ions, present on the surface of the ash.

Monitoring, mitigation, and verification at sequestration sites: SEQURE technologies and the challenge for geophysical detection

Editors note: SEQURE is a trademark of The National Energy Technology Laboratory. A critical component of the National Energy Technology Laboratorys Sequestration Program is the development of tools that can reliably monitor and quantify the amount of CO2 that leaks to the surface. One major requirement for the commercial application of geologic sequestration is accurate leak detection; i.e., leak monitoring and accurate estimation of leak volumes through continued monitoring. This is essential to assure that long-term sequestration is achieved. Significant leakage from the sequestration reservoir defeats the purpose of sequestration, which is to stabilize and then reduce atmospheric concentrations of CO2 for several hundreds to thousands of years. Multiple investigators have attempted to estimate the amount of leakage that is acceptable (e.g., Pacala, 2002; Hepple and Benson, 2002; Dooley and Wise, 2002; Herzog, 2002). Their estimates vary considerably, and range from 1% to 0.01% per annum which leads to leakage of 50% of the injected CO2 volume in 70 to 7000 years, respectively.

Surface characterization of alkali-treated coals

The surface interactions of alkali with coal and mineral matter have been studied by electron spectroscopy for chemical analysis (ESCA) to establish a basis for predicting the relative reactivity of alkali with sulphur during coal beneficiation processes. The speciation of sulphur in coals doped with various alkali salts was determined and quantified after heating the mixtures to 648 K in air or N2, then washing with water. Organic and pyritic sulphur on the surface react with alkali when heated, and the sulphide or oxidized sulphur product can then be washed from the coal. The extent of reaction between the alkali salt and surface sulphur is governed by the size of the cation and the electronic properties of the anion; larger alkali cations are more effective in promoting the reactivity of surface sulphur, as are anions with stronger nucleophilic properties.

Ground-penetrating radar survey and tracer observations at the West Pearl Queen carbon sequestration pilot site, New Mexico

The potential for leakage of injected CO2 at carbon sequestration sites is a significant concern in the design and deployment of long-term carbon sequestration efforts. Effective and reliable monitoring of near-surface environments in the vicinity of these sites is essential to ensure the viability of sequestration activities as well as long-term public and environmental safety. Identification of geologic features (such as faults, fracture zones, and solution enhanced joints that might facilitate release of injected CO2 back into the atmosphere) is a key step in this process. This study reports on near-surface geologic and geophysical characterization efforts conducted at the Department of Energy National Energy Technology Laboratory (NETL) West Pearl Queen carbon sequestration pilot site in southeastern New Mexico, USA, and their use for uncovering possible mechanisms associated with escape of small amounts of perfluorocarbon tracers injected with the CO2.

Surface Spectroscopic Studies of Factors Influencing Xanthate Adsorption on Coal Pyrite Surfaces

The relative adsorption of fluoroxanthates on several different coal pyrites has been found to depend on the degree to which the pyrite surfaces are oxidized. Maximum xanthate adsorption occurs in the absence of pyrite surface oxidation and is affected by the presence of polysulfides and metal-deficient sulfides on the pyrite surface. The structure and electronic properties of the xanthate molecule may also affect its adsorption. 3-(Trifluoromethyl)benzyl xanthate was found to selectively adsorb on pyrite vs. coal surfaces. Secondary ion mass spectrometry is a viable alternative to x-ray photoelectron spectroscopy for detecting xanthate adsorption.

Measurement of methane emissions from abandoned oil and gas wells in Hillman State Park, Pennsylvania

ABSTRACT Abandoned oil and gas wells, improperly plugged or unplugged, present a risk to current and future oil and gas development because they provide a potential pathway for unwanted gas and fluid migration to the surface. The appropriate emission factor for gaseous emissions from these wells is uncertain, as a limited number of studies have reported abandoned wells as a methane emissions source. A helicopter-based survey that mapped methane concentration and located wells by detecting magnetic anomalies was conducted in Hillman State Park in southwestern Pennsylvania. Although well finding via aerial survey was successful, elevated methane concentrations due to emissions from wells in the survey area were not detected by helicopter as abandoned wells were likely too small a source of methane to detect from elevations that helicopters fly at (tens of meters). Measurement of methane emission rates from 31 wells were collected using several techniques that are compared and evaluated for their effectiveness: Hi Flow sampler, field-portable flame ionization detector, infrared camera, dynamic flux chamber and bag sampling. Nine of the 31 wells were buried; average methane flux for these wells was not statistically different from the background. Mass flow rate from the remaining 22 wells ranged from non-detection (less than 0.09 kg CH4/day) to 4.18 kg CH4/day with a mean of 0.70 kg/well/day (median of 0.24 kg CH4/day/well) and a sample standard of error of 0.21 kg CH4/well/day. This emission factor, while not intended for exclusive use in developing a methane emissions inventory for abandoned oil and gas wells, contributes to the growing amount of methane emissions data for this source category. The results from the aerial survey, ground-based well location verification and emissions measurements, and the evaluation of measurement approaches described here, provide a comprehensive characterization of abandoned wells in one field that can inform future measurement studies.