Fuel
The applicability of the reflectance micro-Fourier transform infrared (FT-i.r.) technique to analyse the distribution of functional groups in coal is discussed. The spectra of a series of coals from lignite to anthracite obtained using reflectance micro-FT-i.r. were compared with those of the same materials but obtained using transmission micro-FT-i.r. and KBr pellet techniques. This comparison...
An efficient method is described for the recovery of wax from lignite tar by solvent extraction followed by isolation of the wax from the extract. Light petroleum (boiling range 60-80°C) was used as the solvent. Under optimum conditions (i.e. solvent:feed ratio = 4 and time of reflux 1 h at 70°C), up to 85% of the tar could be extracted. In the next stage, almost the entire amount of wax present...
The results are reported of detailed physical characterization of six ashes from coals representative of those burned in US power plants. Centrifugal separation was used to classify the ashes into six density categories in the range < 1.6 to > 3.2 g cm - 3 . The size distributions of all density classes were determined in the range 1-200 μm. For most of the density classes, log-normal...
The solute-solid adsorption isotherms (SSA) of asphaltenes and resins were measured using the inorganic fraction (97% SiO 2 ) of the deposit that plugged the tubing of a production well as an inorganic adsorbent. In other experiments, Ceuta asphaltenes and the product (HA) of heating them at 350°C for 11 h were used as organic adsorbents in heptane, toluene and heptane-toluene at 26°C. Ceuta...
An improved one-dimensional model for countercurrent oxidation and gasification of coal in fixed or slowly moving beds has been developed. The model incorporates an advanced devolatilization submodel that can predict the evolution rates and the yields of individual gas species and tar. A split, back-and-forth, shooting method is implemented to satisfy exactly the boundary conditions for both the...
Previous chemical equilibrium calculations as well as experimental results concerning cocombustion of high sulfur containing fuels and biomass fuels have shown that a significant retention of sulfur can be obtained in the ash. The processes are, however, complex and to minimize the SO 2 emissions, experiments were performed, according to statistical experimental designs, in a small pilot...
The accuracy of the loss-on-ignition (LOI) test to determine the content of unburned carbon in fly ash samples was evaluated by thermogravimetry. Evaluations were performed on fly ash from a stoker boiler, a pulverized coal boiler, an atmospheric fluidized bed boiler and a pressurized fluidized bed boiler. The fly ashes from the fluidized bed boilers were found to contain significant quantities of...
Three infrared spectroscopic methods--photoacoustic, diffuse reflectance and transmission--were evaluated for the qualitative analysis of carbon fibres. Transmission spectra of a potassium bromide (KBr) pellet detect the bulk of a carbon fibre, and are subject to interference by water in the KBr pellet. Extensive dehydration of a KBr pellet at elevated temperatures may cause chemical changes. In...
The amount of residual, or unburned, carbon in fly ash is an important concern in the design and operation of pulverized coal fired boilers. Char oxidation is the slowest step in the coal combustion process, and the rate at which this heterogeneous reaction proceeds has an important effect on the degree of carbon burnout. There is an extensive literature on char combustion kinetics based on data...
Least square analysis of the X-ray absorption near edge structure (XANES) region of sulfur K edge X-ray absorption fine structure (XAFS) spectra can provide a quantitative analysis of both the organic and inorganic functional forms of sulfur in coal. In the current article, this method is applied to speciation of the sulfur forms in a number of desulfurized coals. The samples investigated include...
Rapid hydropyrolysis product yields were determined using a heated-grid apparatus for coals ranging from lignite to lower bituminous in rank. Least-squares regression analysis showed that there are significant correlations of total yield with, in order of decreasing correlation coefficient, BS volatile matter, O/C atomic ratio, vitrinite reflectance, and carbon content. In addition, the yield of...
Seven process variables--retort temperature, solids recycle ratio, char content of recycle solids, recycle solids temperature, pretreatment of recycle solids with ammonia, solids residence time and steam concentration--were studied. The Plackett-Burman statistical experimental design, highly effective for detecting main effects of large number of variables with a minimum number of experiments, was...
Experiments were conducted in an externally heated drop-tube furnace to assess the effectiveness of the chemical calcium magnesium acetate [CMA, CaMg 2 (CH 3 COO) 6 ] as a combustion catalyst and a coal pretreatment agent for reducing SO 2 emissions. Bituminous coal particles of two distinct sizes, pulverized (75-90 μm) or micronized and beneficiated (mean diameter...
Much of the natural gas in the Devonian shales in the Appalachian basin is stored as a condensed phase, which may be in solution in organic material or adsorbed on surfaces. A laboratory apparatus and measurement procedures for accurate determination of the relatively small amounts of condensed phase typical of Devonian shale samples have been designed. A temperature control system was developed...
The effect of the presence of hydrogen donor diluents on visbreaking (VB) process performances were examined, performing comparative tests under different reaction severities. Results of experiments carried out at bench-scale level, with a vacuum residue of Belaym crude, confirm that the VB performances can be substantially improved by adding hydrogen donor solvents. Provided a proper donor is utilized,...
Flash pyrolysis of wood in a circulating fluidized bed is studied. The results of a comprehensive gas-solid reaction model are used successfully in analysing the system. The changes in the structure, the transient nature of heat and mass transfer and the reaction scheme are accounted for. All the structural parameters and thermophysical properties are used as continuously changing variables.
This paper describes the feasibility of using fluorescence microscopy in conjunction with normal white light microscopy and image analysis in order to carry out fully automated maceral analysis. A short review of current image systems shows a lack of success in distinguishing the liptinite species from the resin media used to form the coal block. Fluorescent lighting is commonly used during manual...
The thermal stability of humic substances (humic acids, sodium humate and ammonium humate) manufactured on the plant or pilot plant scale was examined within the temperature range 150-250°C with a period of heating up to 60 min. Under these conditions no significant destruction of the skeleton of the humic substances occurs; in spite of a certain loss in weight, these materials retain the fundamental...
ZSM-5 zeolites were modified with copper and platinum by ion exchange and during the process of hydrothermal zeolite synthesis. The catalytic activity of the prepared Pt and Cu ZSM-5 zeolite catalysts was tested for complete oxidation of propane. It was observed that the mode of introduction of metals into the zeolite and the metal content influenced the catalytic activity. Copper introduced into...
Heating of iron powder containing carbon with aqueous alkali metal salt solution at 300°C gave a mixture of C 1 -C 6 hydrocarbons and acetone. Prolonged reaction of the iron powder with aqueous potassium carbonate solution gave larger amounts of hydrocarbons and acetone than the reaction with aqueous potassium hydroxide solution.