Effect of temperature, sample size and gas flow rate on drying of Beulah-Zap lignite and Wyodak subbituminous coal

Beulah-Zap lignite and Wyodak-Anderson ([minus]100 and [minus]20 mesh from the Argonne Premium Coal Sample Program) were dried in nitrogen under various conditions of temperature (20--80[degree]C), gas flow rates (20--160 cc/min), and sample sizes (20--160 mg). An equation relating the initial drying rate in the unimolecular mechanism was developed to relate the drying rate and these three variables over the initial 80--85% of the moisture loss for the lignite. The behavior of the Wyodak-Anderson subbituminous coal is very similar to that of the lignite. The nitrogen BET surface area of the subbituminous sample is much larger than the lignite

Acoustic Microscopy of Ceramics

The scanning laser acoustic microscope (SLAM) is applied to the problem of nondestructive testing of ceramic materials. The employment of a very high resolution ultrasonic imaging instrument provides capabilities which supplement ultrasonic pulse-echo testing. In addition, by means of showing a picture of the flaw, the SLAM technique provides its own capabilities which alleviate some of the limitations of other techniques. Flaws of various types are documented in this paper

Drying of Beulah-Zap Lignite

Lignite dried in a stream of dry nitrogen at moderate temperatures (20-80-degrees-C) loses water in two distinguishable modes. The first mode represents about 80-85% of the loss of moisture. The second represents the other 15-20% lost under these conditions. The rate follows a unimolecular mechanism (like radioactive decay) for each mode. The activation energy for the first mode is close to the heat of vaporization of water. The rate is dependent upon the gas flow around the sample and the weight (or thickness) of the sample. Work at Amoco Oil Company indicated that the oil yield was higher for the dried coal than for raw or partly dried lignite. Work at Southern Illinois University showed that the mechanism was the same when differential scanning calorimetry was used to follow the kinetics of drying. Other work at the University of Southern Mississippi showed that the physical structure of the lignite (measured by X-rav diffraction) is measurably different for the dried and raw materials

Non-intrusive heat flux measurements using ultrasound

Papers presented to the 11th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 20-23 July 2015.Heat flux values are needed in the field of fluid mechanics and heat transfer to quantify the transfer of heat within systems. Maximizing or minimizing the thermal energy transfer in many systems is crucial to their optimization. In this study, we demonstrate how heat flux measurements can be made using ultrasound. Tests have been conducted on a series of metals heated at one end using a calibrated infrared source. Using ultrasonic sensors located remotely from the heated surface the time-of-flight variations of heated surface echoes are used to calculate heat flux. The temporal variation of heat flux determined using ultrasonic data is identical to that derived from transient thermal models. In this study the value of ultrasonicbased heat flux estimates were found to be in good agreement with independent estimates computed from thermal transport models.am201

Assessment of hydropyrolysis as a method for the quantification of black carbon using standard reference materials

A wide selection of thermal, chemical and optical methods have been proposed for the quantification of black carbon (BC) in environmental matrices, and the results to date differ markedly depending upon the method used. A new approach is hydropyrolysis (hypy), where pyrolysis assisted by high hydrogen pressures (150 bar) facilitates the complete reductive removal of labile organic matter, so isolating a highly stable portion of the BC continuum (defined as BChypy). Here, the potential of hypy for the isolation and quantification of BC is evaluated using the 12 reference materials from the International BC Ring Trial, comprising BC-rich samples, BC-containing environmental matrices and BC-free potentially interfering materials. By varying the hypy operating conditions, it is demonstrated that lignocellulosic, humic and other labile organic carbon material (defined as non-BChypy) is fully removed by 550 °C, with hydrogasification of the remaining BChypy not commencing until over 575 °C. The resulting plateau in sample mass and carbon loss is apparent in all of the environmental samples, facilitating BC quantification in a wide range of materials. The BChypy contents for all 12 ring trial samples fall within the range reported in the BC inter-comparison study, and systematic differences with other methods are rationalised. All methods for BC isolation, including hypy are limited by the fact that BC cannot be distinguished from extremely thermally mature organic matter; for example in high rank coals. However, the data reported here indicates that BChypy has an atomic H/C ratio of less than 0.5 and therefore comprises a chemically well-defined polyaromatic structure in terms of the average size of peri-condensed aromatic clusters of >7 rings (24 carbon atoms), that is consistent across different sample matrices. This, together with the sound underlying rationale for the reductive removal of labile organic matter, makes hypy an ideal approach for matrix independent BC quantification. The hypy results are extremely reproducible, with BChypy determinations from triplicate analyses typically within ±2% across all samples, limited mainly by the precision of the elemental analyser

Ash deposition propensity of coals/blends combustion in boilers: a modelling analysis based on multi-slagging routes

A method that is based on the initial slagging routes and the sintered/slagging route has been developed and used for predicting the ash deposition propensities of coal combustion in utility boilers supported by the data collected from power stations. Two types of initial slagging routes are considered, namely (i) pyrite-induced initial slagging on the furnace wall, and (ii) fouling caused by the alkaline/alkali components condensation in the convection section. In addition, the sintered/slagging route is considered by the liquids temperature, which represents the melting potential of the main ash composition and is calculated using the chemical equilibrium methods. The partial least square regression (PLSR) technique, coupled with a cross validation method, is employed to obtain the correlation for the ash deposition indice. The method has been successfully applied to coals/blends combustion in boilers, ranging from low rank coals to bituminous coal. The results obtained show that the developed indice yields a higher success rate in classifying the overall slagging/fouling potential in boilers than some of the typical slagging indices. In addition, only using the SiO2/Al2O3 ratio to predict the melting behaviors and slagging potential is inaccurate since the effect of the SiO2/Al2O3 ratio is dictated by both the original ash composition and the way in which the SiO2/Al2O3 ratio is changed. Finally, the influence of the acid components (SiO2 and Al2O3) on the ash deposition prediction is investigated for guiding the mineral additives. It is noticed that the predicted ash deposition potentials of the three easy slagging coals investigated decrease more rapidly by adding Al2O3 than by adding SiO2

Ion exchange and adsorption on low rank coals for liquefaction

The objectives of this program involve the study of the catalysis of liquefaction of low rank coals. Ion exchange and adsorption techniques are being used or modified to incorporate catalytically active metals into coal samples. Relative oil yields will be determined by Sandia National Laboratory and PETC collaborators to establish the effectiveness of the catalyst incorporation techniques. This report describes work done over the past 12 months of an on-going project

Evidence for the Tribochemical Generation of Hydrogen From Higher Rank Coals

Analysis of gases in sealed ampoules of higher rank Argonne Premium Coal Samples over a period of years has revealed the presence of significant (up to about 18%) constant amounts of hydrogen and increasing amounts of carbon dioxide. Comparison with the gas contents of sealed 55 gallon drums which have not been pulverized indicates that these gases came from activity following the collection of the samples. Several hypotheses are examined. The evidence indicates a possible tribochemical reaction involving fresh surface generated during pulverizing in the nitrogen atmosphere. It is probable that water reacts with the coal surface to release hydrogen. The oxygen from the water appears to bound to active sites, and later diffusion leads to formation and release of carbon dioxide

Effect of temperature, sample size and gas flow rate on drying of Beulah-Zap lignite and Wyodak subbituminous coal

Beulah-Zap lignite and Wyodak-Anderson ({minus}100 and {minus}20 mesh from the Argonne Premium Coal Sample Program) were dried in nitrogen under various conditions of temperature (20--80{degree}C), gas flow rates (20--160 cc/min), and sample sizes (20--160 mg). An equation relating the initial drying rate in the unimolecular mechanism was developed to relate the drying rate and these three variables over the initial 80--85% of the moisture loss for the lignite. The behavior of the Wyodak-Anderson subbituminous coal is very similar to that of the lignite. The nitrogen BET surface area of the subbituminous sample is much larger than the lignite