Showing papers on "Coal published in 1981"

Multiple-site underground magnetic heating of hydrocarbons

Abstract: A first underground deposit of lignite or coal is heated by magnetic induction to recover hydrocarbon liquids and gases. The carbon remaining is combusted with air and steam to produce a gas which is combusted to generate electrical energy. The electrical energy is transmitted to second underground deposits of oil shale, tar sand or heavy oil, and is used to heat the second deposits in order to recover hydrocarbon liquids and gases.

Mechanism of Hydrocarbon Synthesis over Fischer-Tropsch Catalysts

Abstract: Publisher Summary This chapter discusses the mechanism of hydrocarbon synthesis over Fischer-Tropsch catalysts. The superiority of liquid over gaseous energy carriers, in particular for automotive purposes, resides in the high energy density of liquids and the relatively low weight of the required container. When compared to solid fuels such as coal, liquids have the advantage that pollutants can be removed more easily, and transport through pipelines or in tankers is cheap and efficient. The chemistry of the catalytic processes is, of course, independent of the way in which the synthesis gas was manufactured; besides coal gasification the steam re-forming of natural gas is a well-known route to produce synthesis gas, although with a higher H 2 /CO ratio. It is convenient to distinguish methanation, where methane is the predominant product, and the Fischer- Tropsck process directed toward the manufacture of predominantly liquid hydrocarbons. However, as the product composition for a given catalyst largely depends on the conditions, the term Fischer-Tropsck catalysis is used also for those cases in which, owing to the variation of one or more of these parameters, the product is mainly gaseous or solid at room temperature and atmospheric pressure.

Vaporization and condensation of mineral matter during pulverized coal combustion

Abstract: The factors governing the amount and properties of the submicron aerosol (fume) produced on combustion of coal have been studied by burning size-graded Montana lignite particles in a laminar drop-tube furnace at 1750 K. The coal particle temperatures achieved vary from 1800 K to 2800 K as the oxygen concentration in which the particles burn is increased from 5% to 100%. Size fractionation of the ash yields a bimodal size distribution. The average size of the fine particles varies from less than 50diameter to greater than 300 , depending on the combustion conditions. These fine particles are produced by vaporization of the mineral matter species during combustion and their subsequent recondensation. The amount of fume produced as metal oxides increases from 0.1% of the total ash at particle temperatures around 1800 K to 20% at 2800 K. The chemical composition of the Montana lignite fume is dominated by the refractory oxides MgO and CaO at all but the lowest temperatures (T The oxidation of the vaporized reduced-state species away from the particle surface results in a supersaturation of the refractory oxides, leading to their nucleation. A simple model in which growth of these particles then occurs by coalescent collisions and by heterogeneous condensation of new material released from the burning particles provides a good representation of the observed particle sizes as a function of residence time and degree of ash vaporization.

Coal-block-gasification experiments: laboratory results and field plans

Abstract: The ability to visually inspect in situ gasification cavities has hindered our understanding of the process. As a step in overcoming this problem, laboratory-scale steam/oxygen gasification of 300-kg coal blocks were performed using an initial drilled link. At the end of the experiments the cavities were examined. For the three coals studied (Wyodak, Hanna, and WIDCO), the cavities were quite different, yet the product-gas heating values were similar. Detailed results of these tests are presented. Concern over the ability to scale small experiments to a large field system led to a proposal to perform intermediate-scale tests at an exposed coal face. The test plan for the first intermediate-scale tests, to be performed at the WIDCO mine site, is outlined.

Controlled retracting injection point (CRIP) system: a modified-stream method for in situ coal gasification

Abstract: The underground coal gasification process, in practice, is subject to various problems that make it difficult to maintain and control an efficient long-term operation. One of the major problems is the need to move the injection point (where the combustion-supporting air or oxygen from the surface is fed into the coal seam) to new areas of unburned coal as the burn progresses. To achieve better control of the gasification process, we recommend the controlled retracting injection point or CRIP system. The controlled retracting injection point or CRIP system is designed to keep the injection point on the bottom of the coal seam and to move it backwards away from the collapse zone into fresh, solid coal. The principle of controlled retraction allows the operator to choose the optimum time and distance to move the injection point, and consequently the burn zone, to get the best possible performance from the gasifier. Although this system will work with coal seams of any thickness, it is particularly well suited to thick coal seams where the cavity grows by coal collapse as well as combustion. Placement of the production channel at the top of the seam above the injection well ensures isolation from themore » effects of collapse and reduces the risk of plugging the production well.« less

Direct Observations of Devolatilizing Pulverized Coal Particles in a Combustion Environment

Abstract: Direct observations of the early stages of combustion of size-graded (≈100μm) pulverized coal particles are reported. The particles are introduced on the centerline, of a high temperature, transparent, laminar flow reactor fed by a gas fueled, premixed flat flame. Photographs of particle emission, high magnification shadowgraphs of burning particles, and micrographs of partially burnt captured material have been obtained. The ignition of both bituminous coal and lignite subjected to rapid heating (≈105K/sec) by hot combustion products is characterized by, bright diffuse emission attributed to burning of ejected volatile matter. After approximately 5 msec this emission ceases, and incandescence attributed to heterogeneous char oxidation is observed. Shadowgraphs and micrographs of burning bituminous coal indicate that, coincident with ignition, ejected volatile matter forms a condensed phase surrounding the particle. The condensed phase is evidently a soot-like material resulting from pyrolytic cracking of hydrocarbons in the volatile matter. Viscous drag forces cause the condensed material to be swept into laminar wake structures which eventually separate from the particles. Under oxidizing conditions this condensed volatile matter is oxidized during the early stages of char burning, while under reducing conditions it persists throughout the flow reactor. Although burning lignite appears similar to bituminous coal in emission, shadowgraphic and micrographic observations, indicate that a condensed phase is not formed during devolatilization. Nor are, changes in particle size or shape observed during the earliest stages of combustion. These observations are consistent with previous results which showed that bituminous coal volatiles contain large fractions of soot producing heavy hydrocarbons, while lignite volatiles are largely composed of CO, CO2, H2, H2O and light hydrocarbons. The observations are also consistent with differences in the pore structure and swelling properties of the two coasl.

Kinetics of the removal of iron pyrite from coal by microbial catalysis.

Abstract: Different strains of Thiobacillus ferrooxidans and Thiobacillus thiooxidans were used to catalyze the oxidative dissolution of iron pyrite, FeS2, in nine different coal samples. Kinetic variables and parametric factors that were determined to have a pronounced effect on the rate and extent of oxidative dissolution at a fixed Po2 were: the bacterial strain, the nitrogen/phosphorus molar ratio, the partial pressure of CO2, the coal source, and the total reactive surface area of FeS2. The overall rate of leaching, which exhibited a first-order dependence on the total surface area of FeS2, was analyzed mathematically in terms of the sum of a biochemical rate, {nu}1, and a chemical rate, {nu}2. Results of this study show that bacterial desulfurization (90 to 98%) of coal samples which are relatively high in pyritic sulfur can be achieved within a time-frame of 8 to 12 days when pulp densities are ≤20% and particle sizes are ≤74 µm. The most effective strains of T. ferrooxidans were those that were isolated from natural systems, and T. ferrooxidans ATCC 19859 was the most effective pure strain. The most effective nutrient media contained relatively low phosphate concentrations, with an optimal N/P molar ratio of 90:1. These results suggest that minimal nutrient additions may be required for a commercial desulfurization process.

Computer models to support investigations of surface subsidence and associated ground motion induced by underground coal gasification

Abstract: Two computer codes compare surface subsidence induced by underground coal gasification at Hoe Creek, Wyoming, and Centralia, Washington. Calculations with the STEALTH explicit finite-difference code are shown to match equivalent, implicit finite-element method solutions for the removal of underground material. Effects of removing roof material, varying elastic constants, investigating thermal shrinkage, and burning multiple coal seams are studied. A coupled, finite-difference continuum rigid-block caving code is used to model underground opening behavior. Numerical techniques agree qualitatively with empirical studies but, so far, underpredict ground surface displacement. The two methods, numerical and empirical, are most effective when used together. It is recommended that the thermal characteristics of coal measure rock be investigated and that additional calculations be carried out to longer times so that cooling influences can be modeled.

Laboratory-scale simulation of underground coal gasification: experiment and theory

Abstract: LLNL has been conducting laboratory-scale experiments simulating underground coal gasification in order to better understand the physical and chemical phenomena governing the process. A 1 cm borehole is drilled through a block of coal which is cut to fit in a 55 gallon oil drum. Inlet gas may be air or oxygen/steam mixture at various ratios. The blocks are burned for a period of several hours at a prescribed flow schedule, with appropriate instrumentation. Gas quality is found to be relatively independent of coal type for the range of sub-bituminous coals tested. After the burn the blocks of coal are cut open to examine the cavity. A mathematical modeling effort supports these experiments. So far the models have been restricted to pure carbon, to simplify the chemistry in the model. No steam/char reaction is modeled. Only the carbon/oxygen surface reaction is allowed, hence the growth of the cavity wall is limited by the rate of transport of oxygen to the wall. When plug flow is assumed in the cavity the model predicts reasonable cavity shape downstream, but an incorrect shape upstream. When aerodynamic flow, including viscosity and vortex formation, is calculated in the cavity reasonable cavity shapes are obtained.

Technology of the Fischer-Tropsch Process

Abstract: Sasol One, formerly known as South African Coal, Oil, and Gas Corp., operates a plant for the production of liquid fuels, pipeline gas, and chemical products from coal in Sasolburg in the province of the Orange Free State in South Africa. This plant started production in 1955 and today Sasol has 25 years' practical experience with the production of synthesis gas via Lurgi coal gasification and the synthesis of hydrocarbons by the Fischer-Tropsch process. In 1975 the decision was taken to build a much larger Fischer-Tropsch plant, mainly for the production of motor fuels, and this plant is at present being commissioned. The first final products from this plant will become available to the public early in the second half of 1980. The continuing increase in crude oil prices and instability on the oil supply market were the incentives for the decision in 1979 to build anther Sasol plant practically identical to Sasol Two. Construction on this Sasol Three plant is well under way and it is expected to ...

The thermal decomposition of pulverized coal particles

Abstract: The physical, thermal, and chemical behavior of pulverized coal particles during thermal decomposition are examined for five coal types and two particle sizes for one of the bituminous coals. Particles were injected axially into a lean (35% excess air) methane/air flat flame with a nominal peak temperature of 1750°K. The significant events observed are classified by three time scales. Particles heat to the gas temperature in less than 10 msec, devolatilization occurs between 10 and 75 msec and, under the appropriate conditions, large soot particles are formed WRS and grow for times exceeding 75 msec. The events that accompany devolatilization are dependent upon coal type and particle size. For large bituminous particles (ca., 80 μm) a significant volatile fraction is ejected from the particle as a jet. This volatile jet reacts close to the particle producing a trail of small solid particles. The local heat released during the reaction of the volatiles, in combination with heterogeneous oxidation, increases the particle, temperature and raises it above that of the bulk gas stream. At later times, large soot structures, are formed which are attributed to the agglomeration of small, homogeneously formed soot on the volatile trail structures. Small bituminous particles (ca., 40 μm) burn with a higher intensity (i.e., higher temperature and more rapidly) with few trails and do not produce soot structures probably because of the more diffuse nature of the devolatilization process. Other ranks of coal exhibit different physical, thermal, and chemical behavior. For example, neither the lignites nor the anthracite produce volatile trials. Further, the particle temperature for the lignites is only slightly shifted above the bulk gas temperature in the devolatilization region while anthracite takes 50 msec to reach the bulk gas temperature level. This is attributable to the relatively low heat content of the volatiles in the former case and the low volatile content in the latter. The impact of the above observations on the formation of fuel NO is discussed.

A Fourier Transform Infrared Study of Mineral Matter in Coal: The Application of a Least Squares Curve-Fitting Program

Abstract: The application of Fourier transform infrared spectroscopy to the quantitative determination of mineral matter in coal is discussed. The use of a least squares curve-fitting program allows a choice between standards to be made. The results of an analysis of mineral mixtures and a coal low temperature ash are presented. The results are in good agreement with known concentrations and those obtained by other methods of analysis.

An Electrokinetic Study on the Oil Flotation of Oxidized Coal

Abstract: The objective of this investigation was to study the electrokinetic behavior of oxidized coals and of hydrocarbon emulsion droplets of flotation reagents to indicate the feasibility of separating the oxidized coals from ash materials and pyrite by an oil flotation process. The effects of surfactants and hydrolyzed metal ions were also included. The electrokinetic behavior of the oxidized coals and the hydrocarbon emulsion droplets were studied by an electrophoresis technique. Generally the isoelectric point (IEP) of the coals decreased with increasing degree of oxidation. A model of selective flotation of oxidized coal is postulated on the basis of the electrokinetic results. This model simply states that in the presence of a suitable amount of collector and frother, the optimal selective flotation of oxidized coal will occur at the IEP of the oxidized coal. To achieve this condition at the coal surface, it is necessary to adsorb heavy metal hydroxide ions prior to flotation and to absorb hydroca...

Direct method determination of the gas content of coal: procedures and results. Bureau of investigations/1981

Abstract: The explosion hazard of methane-air mixtures has become an increasingly serious mine planning problem, and an advance assessment of methane gas potential can therefore be essential for a safe and economic mine development program. As part of its coal mine health and safety program, the Bureau of Mines has developed a simple, inexpensive test to measure the methane content of coal samples obtained from exploration cores. The gas content of coal per unit weight as determined by the direct method test can be used as a basis for a preliminary estimate of mine ventilation requirements, and to determine if degasification of the coalbed in advance of mining should be considered.

Direct method determination of the gas content of coal: procedures and results

Abstract: The explosion hazard of methane-air mixtures has become an increasingly serious problem in mining, and an advance assessment of methane gas potential is therefore essential for a safe and economic mine development program. As part of its coal mine health and safety program, the Bureau of Mines has developed a simple, inexpensive test to measure the methane content of coal samples obtained from exploration cores. The gas content of coal per unit weight as determined by the direct method test can be used as a basis for a preliminary estimate of mine ventilation requirements, and to determine if degasification of the coalbed in advance of mining should be considered. The results of 583 direct method tests are summarized in tabular form. These results include data on the gas content of 125 coalbeds in 15 states.

A Technological Perspective for Catalytic Processes Based on Synthesis Gas

Abstract: Continuously increasing oil prices, a dwindling supply of indigenous petroleum, and the existence of extensive coal reserves has made the conversion of coal to chemicals and clean-burning fuels an increasingly important part of the national energy programs for a number of industrial nations. In particular, there is a growing interest in the production and use of synthesis gas as a feedstock for the manufacture of fuels and chemicals. Most of the proposed routes are catalytic in nature, and are directed at overcoming the limitations of Fischer-Tropsch chemistry, especially selectivity. Over the past several years, research efforts have led to new selective routes to various fuel fractions; to petrochemical feedstocks including light olefins and various aromatics; to commodity chemicals such as ethylene glycol, ethanol, and acetic acid; and to a number of other fuels and chemicals.

O-Alkylation chemistry of coal and its implications for the chemical and physical structure of coal

Abstract: The O-alkylation of coal by the use of a quaternary ammonium hydroxide base and a primary alkyl halide is a general method for the preparation of coal derivatives. These derivatives differ from the starting coal because the weakly acidic protons, primarily those associated with the hydroxyl and carboxylic groups, are replaced by alkyl substituents. The two coals described in this study are Illinois no. 6 coal (Monterey Mine No. 1) and Rawhide coal (Smith Seam in Wyoming). The Illinois No. 6 coal has five and the Rawhide coal has eight weakly acidic protons per 100 carbon atoms, respectively. For each of the two coals, five O-alkylated derivatives were prepared namely, the methyl, n-butyl, benzyl, n-heptyl, and n-octadecyl coal derivatives. The complete O-alkylation of these coals (the reaction of all the available acidic protons) was achieved under ambient conditions and remarkably short reaction times. Infrared analyses of these O-alkylated coals are consistent with ether and ester derivatives of hydroxyl and carboxylic acid functionalities. High-resolution /sup 13/C NMR spectra of the tetrahydrofuran-soluble O-methyl coal derivatives are used to estimate the quantity of extracted ethers and esters. The physical properties of these uniquely modified coals were drastically altered. The elemental composition of eachmore » coal derivative accurately reflected the weight percents expected based on the complete alkylation of all acidic sites of starting coal. Helium density and mercury porosimetry measurements revealed that the secondary structure (intermolecular associations) of the O-alkylated coals was significantly reduced. There was also a dramatic increase in the extractability of coal molecules after O-methylation.« less

Reduction of Nitric Oxide by Coal Char at Temperatures of 1250–1750 K

Abstract: INTRODUCTION An important factor to be considered in developing NO control strategies for pulverized coal combustors is the potential for the reduction of NO by char. Such reaction has been shown to reduce appreciably the emissions of NO from fluidized bed coal combustors (Pereira et al., 1975). A number of experimental studies were carried out of the NO/char reactions using fixed and fluidized bed reactors (Furusawa et al., 1977; Chan, 1977; Sprouse, 1977; Beer et al., 1977) in which the products of the reaction were identified and kinetic parameters of the reaction were determined. The present paper is concerned with the destruction of NO by char at temperatures of interest in pulverized coal flames.