摘要:

The development of electromagnetic systems to detect and monitor coal‐related processes requires a thorough knowledge of the electrical properties (dielectric constant and conductivity) of coal. Using a two‐path interferometer at microwave frequencies (?9 GHz), samples of solid eastern bituminous and eastern anthracite coals were tested as a function of polarization and direction of travel of the electromagnetic wave. Temperature moisture, and pyrite distribution tests were performed on eastern bituminous coal samples. In general there were slight decreases in the values of the dielectric constant and conductivity as a function of temperature, from ambient to 700° F, and as the moisture content decreased through drying. Pyrite layers along the bedding planes cause a general increase in the conductivity. The anthracites (higher rank coals) have larger values of conductivity (about a factor of 10) and permittivity (about a layer of 2 and 3) than bituminous (lower rank) coals. No distinct relationship was found between the direction of propagation and the electrical properties. Recommendations are made for orienting electromagnetic radiators to improve efficiencies of systems which are designed for coal‐related detection, monitoring and mapping applications.

ISSN:0094-243X    

DOI:10.1063/1.32965

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Many advanced fossil energy processes require the continuous transport of crushed coal into high pressure vessels. The most common methods of doing this are sequenced pneumatic injection from pressurized lock hoppers and pumping of a coal‐liquid slurry. Operation of these and other coal feeding systems is outlined and standard instrumentation for monitoring coal feed is reviewed. Applicable new and developmental instrumentation is discussed.

ISSN:0094-243X    

DOI:10.1063/1.32966

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The Mo¨ssbauer spectroscopic technique has been adapted to provide a reliable measurement of pyritic sulphur in coal. The Mo¨ssbauer method is quick, nondestructive, and adaptable to automation. It can be applied hindering the use of Mo¨ssbauer spectroscopy for pyritic measurements have been resolved. Sample homogenization techniques consistent with the spectroscopic requirements were developed. A sample holder compatible with a 5 to 10 g coal sample was designed. Two calibration curves were evaluated: one based on a mixture of pyrite and graphite, the other on HCl‐leached coal. A simple correction method for the effects of ash absorption was demonstrated. Differences between the Mo¨ssbauer and ASTM wet chemical methods for analyzing pyritic sulphur in coal were evaluated. Good agreement was shown, provided residual undissolved pyritic in the ASTM method is taken into account. Analysis of spectrometr capability indicates a routine sample could be analyzed in about 10 minutes.

ISSN:0094-243X    

DOI:10.1063/1.32968

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The reaction of CO and H2to produce CH4has been studied at high pressures over Ni(100) and Ni(111) surfaces using a microcatalytic reactor system and Auger Spectroscopy. It has been found that theratepersurfaceNiatomis identical on the two crystal planes and is very similar to the specific rate on high area supported Ni catalysts. In addition, the activation energy is independent of Ni catalyst structure. Auger spectroscopy has been used to characterize the surface carbon produced by CO decomposition on Ni, and it is concluded that a carbidic form of carbon is an intermediate in the catalytic synthesis of CH4over Ni.

ISSN:0094-243X    

DOI:10.1063/1.32941

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Various mechanisms have been invoked in the past to explain the effects of catalysts on the gasification reactions of carbon. However in many cases the observed catalytic behavior can be interpreted in terms of oxidataion‐reduced cycles occurring on the carbon surface. This paper describes how the techniques of thermal analysis, together with the predictions of thermodynamics, have proved useful in identifying the sequential steps involved in the catalytic processes.

ISSN:0094-243X    

DOI:10.1063/1.32942

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Increasing costs and declining reserves of petroleum are forcing oil importing countries to develop alternate energy sources. The direct liquefaction of coal is currently being investigated as a viable means of producing substitute liquid fuels. The coal liquids derived from such processes are typically high in nitrogen, oxygen and sulfur besides having a high aromatic and metals content. It is therefore envisaged that modifications to existing petroleum refining technology will be necessary in order to economically upgrade coal liquids. In this review, compositional data for various coal liquids are presented and compared with those for petroleum fuels. Studies reported on the stability of coal liquids are discussed. The feasibility of processing blends of coal liquids with petroleum feedstocks in existing refineries is evaluated. The chemistry of hydroprocessing is discussed through kinetic and mechanistic studies using compounds which are commonly detected in coal liquids. The pros and cons of using conventional petroleum refining catalysts for upgrading coal liquids are discussed.

ISSN:0094-243X    

DOI:10.1063/1.32943

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Coal is a heterogeneous, hydrogen‐deficient, organic rock. In order to convert to an environmentally acceptable liquid fuel, it is necessary to: (1) add hydrogen; (2) hydrocrack to lower the molecular weight; (3) remove sulfur, nitrogen and oxygen; and (4) separate unconverted coal and mineral residues. Catalysts that are selective for increased oil production without concomitant gas formation are highly desirable. Certain naturally occurring minerals in coal, such as pyrite and clay, have been shown to enhance the liquid yield and product quality. Several high‐volatile bituminous coals (KY No. 11, IL No. 6, WV, PA, etc.), with similar petrographic composition, were liquefied at 425 °C for 30 min. with creosote oil as solvent. As the mineral content of the feed coal increased from 5 to 24 percent, the conversion to benzene solubles increased from 22 to 74 percent. Similar trends were observed when pyrite (pulverized to minus five microns) was added to an Illinois No. 6 coal, which was then liquified at 425 °C using SRC‐II heavy distillate as the solvent. These and other mineral matter effects will be discussed, and the concept of disposable catalysts for coal liquefaction will be introduced. A brief description of the pyrite‐to‐pyrrhotite transformation will be given.

ISSN:0094-243X    

DOI:10.1063/1.32945

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The value of fundamental research in coal combustions is still regarded as questionable by many concerned with utilization of research results or with providing research support. It is recognized that the record of the utility of fundamental research has not been outstanding to date, but it is argued here that this is very largely a function of the complexity of the problem which still has not been fully recognized, and the need for those computational facilities that have only become sufficiently available in the last decade or so. Three examples of effective modeling are discussed: the boiler flame, the one‐dimensional char flame, and the fixed‐bed gasifier that have identified important mechanisms with evident implications for utility of the results. A particular feature of the work discussed is the use of parsimoneous modeling which is shown to be particularly effective in obtaining useful results and in specifying priorities for future research. The importance of coupling experimental verification with the parsimoneous modeling is also emphasized. A particular problem identified, as an example of the evaluation of research priorities, is the need to understand the way in which the internal surface of coals and chars develop during reaction.

ISSN:0094-243X    

DOI:10.1063/1.32946

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Heat capacity and NMR studies examine the freezing phenomenon and molecular dynamics for water in Illinois bituminous and Wyoming subbituminous coals as well as an Arkansas lignite. For high water content a broad maximum in heat capacity is observed below 273 K. For low water content a continous transition from liquid‐like to solid‐like properties is observed. This latter deviation from the properties of bulk water is attributed to water‐coal surface interactions. Wideline and transient NMR observations on coals containing H2O and D2O suggest a continous change in characteristic times of motion with temperature on a microscopic scale. Observed activation energies for diffusion, &Dgr;&angupr;0.17 eV, are comparable to those for bulk water.

ISSN:0094-243X    

DOI:10.1063/1.32947

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

As the use of coal increases and more fine material is produced by mining and processing, the need for improved methods of coal beneficiation increases. While flotation techniques can help meet these needs, the technique is beset with many problems. These problems involve surface chemical and interfacial properties of the coal‐mineral‐water slurry systems used in coal flotation. The problems associated with coal flotation include non‐selectivity, inefficient reagent utilization, and excessive variablity of results. These problems can be broadely classified as a lack of predictability. The present knowledge of coal flotation is not sufficient, in terms of surface chemical parameters, to allow prediction of the flotation response of a given coal. In this paper, some of the surface chemical properties of coal and coal minerals that need to be defined will be discussed in terms of the problems noted above and their impact on coal cleaning.

ISSN:0094-243X    

DOI:10.1063/1.32948

出版商:AIP    

年代:1981

数据来源: AIP