Equilibrium and volumetric data and model development for coal fluids

During the present reporting period, experimental measurements were obtained on the solubility of carbon monoxide (CO) in selected hydrocarbons using our static type equilibrium cell. Binary mixtures involving CO + n-eicosane (n-C{sub 20}), n-octacosane (n-C{sub 28}), and n-hexatricontane (n-C{sub 36}) were studied at temperatures from 323.2 to 423.2 K and pressures to 104 bar. These data were analyzed using the Soave-Redlich-Kwong and Peng-Robinson equations of state. While a single interaction parameter, C{sub ij}, describes the n-C{sub 20} and n-C{sub 28} measurements within 0.004 in mole fraction over the full temperature range, temperature dependent parameters are required to adequately fit the n-C{sub 36} data. The present data are in reasonable agreement with the earlier measurements of Huang and coworkers in general, deviations within 0.004 in mole fraction are observed

PHASE BEHAVIOR OF LIGHT GASES IN HYDROCARBON AND AQUEOUS SOLVENTS

Under previous support from the Department of Energy, an experimental facility has been established and operated to measure valuable vapor-liquid equilibrium data for systems of interest in the production and processing of coal fluids. To facilitate the development and testing of models for prediction of the phase behavior for such systems, we have acquired substantial amounts of data on the equilibrium phase compositions for binary mixtures of heavy hydrocarbon solvents with a variety of supercritical solutes, including hydrogen, methane, ethane, carbon monoxide, and carbon dioxide. The present project focuses on measuring the phase behavior of light gases and water in Fischer-Tropsch (F-T) type solvents at conditions encountered in indirect liquefaction processes and evaluating and developing theoretically-based correlating frameworks to predict the phase behavior of such systems. Specific goals of the proposed work include (a) developing a state-of-the-art experimental facility to permit highly accurate measurements of equilibrium phase compositions (solubilities) of challenging F-T systems, (b) measuring these properties for systematically-selected binary, ternary and molten F-T wax mixtures to provide critically needed input data for correlation development, (c) developing and testing models suitable for describing the phase behavior of such mixtures, and (d) presenting the modeling results in generalized, practical formats suitable for use in process engineering calculations. During the present period, the Park-Gasem-Robinson (PGR) equation of state (EOS) has been modified to improve its volumetric and equilibrium predictions. Specifically, the attractive term of the PGR equation was modified to enhance the flexibility of the model, and a new expression was developed for the temperature dependence of the attractive term in this segment-segment interaction model. The predictive capability of the modified PGR EOS for vapor pressure, and saturated liquid and vapor densities was evaluated for selected normal paraffins, normal alkenes, cyclo-paraffins, light aromatics, argon, carbon dioxide and water. The generalized EOS constants and substance-specific characteristic parameters in the modified PGR EOS were obtained from the pure component vapor pressures, and saturated liquid and vapor molar volumes. The calculated phase properties were compared to those of the Peng-Robinson (PR), the simplified-perturbed-hard-chain theory (SPHCT) and the original PGR equations. Generally, the performance of the proposed EOS was better than the PR, SPHCT and original PGR equations in predicting the pure fluid properties (%AAD of 1.3, 2.8 and 3.7 for vapor pressure, saturated liquid and vapor densities, respectively)

Equilibrium and volumetric data and model development of coal fluids

The long term goal of our efforts is to develop accurate predictive methods for description of equilibrium phase properties for a variety of types of mixtures and operating conditions. The specific objectives of the work specified herein include: (1) development of an experimental facility having the capability to provide data on equilibrium phase compositions (solubilities) and liquid densities, and doing so with greater accuracy and speed than our previous facility, (2) measurement of equilibrium phase properties for systematically-selected mixtures-specifically those containing important solute gases (such as hydrogen, carbon monoxide, methane, ethane, carbonyl sulfide, ammonia) in a series of heavy paraffinic, naphthenic and aromatic solvents (e.g., n-decane, n-eicosane, n-octacosane, n-hexatriacontane, cyclohexane, Decalin, perhydrophenanthrene, perhydropyrene, benzene, naphthalene, phenanthrene, pyrene), (3) testing/development of correlation frameworks for representing the phase behavior of fluids of the type encountered in coal conversion processes, and (4) generalization of parameters in the correlation frameworks to enable accurate predictions for systems of the type studied, permitting predictions to be made for systems and conditions other than those for which experimental data are available

Phase behavior of coal fluids: Data for correlation development

The effective design and operation of processes for conversion of coal to fluid fuels requires accurate knowledge of the phase behavior of the fluid mixtures encountered in the conversion process. The overall objective of the author's work is to develop accurate predictive methods for representation of vapor-liquid equilibria in systems encountered in coal conversion processes. Objectives include: Measurements of binary vapor-liquid phase behavior data for selected solute gases (e.g. CO{sub 2} and C{sub 2}H{sub 6}) in a series of heavy hydrocarbon solvents to permit evaluation of interaction parameters in models for phase behavior. Measurements on ternary systems in which high-melting-point solvents are dissolved in more volatile aromatics to provide mixed solvents. Evaluation of existing equations-of-state and other models for representation of phase behavior in systems of the type studied experimentally; development of new correlation frameworks as needed. Generalization of the interaction parameters for the solutes studied to a wide spectrum of heavy solvents; presentations of final results in formats useful in the design/optimization of coal liquefaction processes. This quarter, binary solubility data were measured for methane in four aromatic hydrocarbons at temperatures from 323 to 433 K (122 to 320{degree}F) and pressures up to 11.3 MPa (1640 psia). The hydrocarbons studied are: benzene, naphthalene, phenanthrene and pyrene. 23 refs., 9 figs., 10 tabs

Prevalence and molecular epidemiology of Clostridium difficile infection in Indonesia

Clostridium difficile has not been studied in detail in Asia, particularly Southeast Asia. We thus performed a prevalence study across four hospitals in Central Java province, Indonesia. Stool samples were collected from patients with diarrhoea and tested by enzyme immunoassay for glutamate dehydrogenase (GDH) and toxin A/B (C DIFF QUIK CHEK COMPLETE, TechLab). Specimens were cultured and molecular typing was performed. In total, 340 samples were tested, of which 70 (20.6%) were GDH positive, with toxin detected in 19 (5.6%). Toxigenic C. difficile was isolated from 37 specimens (10.9%), while a further 36 (10.6%) nontoxigenic isolates were identified. The most common strain was ribotype 017 (24.3% of 74 isolates), followed by nontoxigenic types QX 224 (9.5%), and QX 238 and QX 108 (both 8.1%). The high prevalence of C. difficile highlights a need for ongoing surveillance of C. difficile infection in Indonesia

Adsorption of Pure Methane, Nitrogen, and Carbon Dioxide and Their Mixtures on San Juan Basin Coal

The major objectives of this project were to (a) measure the adsorption behavior of pure methane, nitrogen, CO{sub 2} and their binary and ternary mixtures on wet Tiffany coal at 130 F and pressures to 2000 psia; (b) correlate the equilibrium adsorption isotherm data using the extended Langmuir model, the Langmuir model, the loading ratio correlation and the Zhou-Gasem-Robinson equation of state; and (c) establish sorption-time estimates for the pure components. Specific accomplishments are summarized below regarding the complementary tasks involving experimental work and data correlation. Representative coal samples from BP Amoco Tiffany Injection Wells No.1 and No.10 were prepared, as requested. The equilibrium moisture content and particle size distribution of each coal sample were determined. Compositional coal analyses for both samples were performed by Huffman Laboratories, Inc. Pure gas adsorption for methane on wet Tiffany coal samples from Injection Wells No.1 and No.10 was measured separately at 130 F (327.6 K) and pressures to 2000 psia (13.7 MPa). The average expected uncertainty in these data is about 3% (9 SCF/ton). Our measurements indicate that the adsorption isotherms of the two coal samples exhibit similar Langmuir-type behavior. For the samples from the two wells, a maximum variation of about 5% in the amount adsorbed is observed at 2000 psia. Gas adsorption isotherms were measured for pure methane, nitrogen and CO{sub 2} on a wet, mixed Tiffany coal sample. The coal sample was an equal-mass mixture of coals from Well No.1 and Well No.10. The adsorption measurements were conducted at 130 F at pressures to 2000 psia. The adsorption isotherms have average expected experimental uncertainties of 3% (9 SCF/ton), 6% (8 SCF/ton), and 7% (62 SCF/ton) for methane, nitrogen, and CO{sub 2}, respectively. Adsorption isotherms were measured for methane/nitrogen, methane/CO{sub 2} and nitrogen/CO{sub 2} binary mixtures on wet, mixed Tiffany coal at 130 F and pressures to 2000 psia. These measurements were conducted for a single molar feed composition for each mixture. The expected uncertainties in the amount adsorbed for these binary mixtures vary with pressure and composition. In general, average uncertainties are about 5% (19 SCF/ton) for the total adsorption; however, the expected uncertainties in the amount of individual-component adsorption are significantly higher for the less-adsorbed gas at lower molar feed concentrations (e.g., nitrogen in the 20/80 nitrogen/CO{sub 2} system). Adsorption isotherms were measured for a single methane/nitrogen/CO{sub 2} ternary mixture on wet, mixed Tiffany coal at 130 F and pressures to 2000 psia. The nominal molar feed composition was 10/40/50. The average expected uncertainty for the total adsorption and CO{sub 2} adsorption is about 5% (16 SCF/ton). However, the low adsorption of nitrogen and methane in this ternary yield average experimental uncertainties of 14% (9 SCF/ton) and 27% (9 SCF/ton), respectively. Limited binary and ternary gas-phase compressibility factor measurements at 130 F and pressures to 2000 psia involving methane, nitrogen, and CO{sub 2} were conducted to facilitate reduction of our ternary adsorption data. These newly acquired data (and available data from the literature) were used to improve the Benedict-Webb-Rubin (BWR) equation-of-state (EOS) compressibility factor predictions, which are used in material balance calculations for the adsorption measurements. In general, the optimized BWR EOS represents the experimental compressibility factor data within 0.5% AAD. The Langmuir/loading ratio correlation (LRC) and the Zhou-Gasem-Robinson (ZGR) two-dimensional EOS were used to analyze the newly acquired adsorption data. Model parameters were obtained for the systems studied. The LRC and ZGR EOS were used to correlate the adsorption data for methane, nitrogen, and CO{sub 2} and their mixtures on wet Tiffany coal. The model parameters were determined by minimizing the sum of squares of weighted errors in the calculated amounts of gas adsorbed. The results demonstrate the ability of the LRC and ZGR EOS to represent the total pure, binary and ternary systems within their expected experimental uncertainties. Specifically, representations with average absolute percentage errors (AAD) of 1-3% (2-15 SCF/ton), 1-8% (1-25 SCF/ton), and 2-10% (7-37 SCF/ton) were obtained for the pure, total binary, and total ternary adsorption isotherms, respectively. However, the quality of fit for the individual-component adsorption varies significantly, ranging from 3% for the more-adsorbed methane or CO{sub 2} to 32% for the less-adsorbed nitrogen. The LRC and ZGR EOS are capable of predicting binary adsorption isotherms based solely on pure-fluid adsorption parameters within twice their experimental uncertainties (1-50 %AAD, 5-40 SCF/ton)

Evaluation of chitosan and carboxymethyl cellulose as ecofriendly corrosion inhibitors for steel

The study was aimed at establishing the possibility of using eco-friendly natural polymers to formulate corrosion inhibitors for sweet oil field environment. Against this background, the performance of two natural polymers; chitosan and carboxymethyl cellulose (CMC) as single component corrosion inhibitors in comparison with a commercial inhibitor formulations, on API 5L X60 pipeline steel in CO2 saturated 3.5% NaCl solution were investigated using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) techniques; complemented with surface morphology characterization of the corroded steel samples without and with inhibitors using scanning electron microscope (SEM). The results indicate that there is a remarkable difference in inhibition efficiency of each inhibitor on the API 5L X60 steel and the commercial inhibitor formulations. Inhibition efficiency increasedwith the increase of inhibitors' concentrations. Immersion timewas found to have a profound effect on the corrosion inhibition performance of all the inhibitors. Also the inhibition efficiency was found to decreasewith the increase in temperature. Potentiodynamic polarization results reveal amixed-type inhibition for all inhibitors. The adsorption of each inhibitor on the steel surface obeys Langmuir's isotherm

Phase behavior of coal fluids: Data for correlation development

During the present report period, our framework for correlating saturation properties using the scaled-variable-reduced coordinate approach was used to develop a correlation for saturated liquid densities of pure fluids at temperatures from the triple point to the critical point. The new correlation results in precise representation of liquid densities of diverse chemical species with average errors of 0.12% when two adjustable parameters are used to characterize each substance. In addition, the proposed model compares favorably with the modified Rackett and the Hankinson-Thomson correlations with the added advantages of covering the full saturation range and obeying scaling-law behavior in the near-critical region. Although the approach is essentially empirical, the results obtained suggest an underlying physical significance for the model parameters and show an excellent potential for generalized predictions. This is demonstrated by the results given here for saturated liquid densities where fully generalized predictions yield average errors of less than 1.0%

Phase equilibrium data for development of correlations for coal fluids

The overall objective of the authors' work is to develop accurate predictive methods for representations of vapor-liquid equilibria in systems encountered in coal-conversion processes. The objectives pursued in the present project include: (1) Measurements of binary vapor-liquid phase behavior data for selected solute gases (e.g., C{sub 2}H{sub 6}, CH{sub 4}) in a series of paraffinic, naphthenic, and aromatic hydrocarbon solvents to permit evaluations of interaction parameters in models for phase behavior. Solubilities of the gases in the liquid phase have been determined. (2) Evaluation of existing equations of state and other models for representations of phase behavior in systems of the type studied experimentally; development of new correlation frameworks as needed. (3) Generalization of the interaction parameters for the solutes studied to a wide spectrum of heavy solvents; presentation of final results in formats useful in the design/optimization of coal liquefaction processes