In the past John W. Patrick has collaborated on articles with Catherine A. Johnson and Manuel J. Gonzalez-Cimas. One of their most recent publications is The strength of industrial cokes: Part 4. The influence of carbonizing conditions on the tensile strength. Which was published in journal Fuel.

More information about John W. Patrick research including statistics on their citations can be found on their Copernicus Academic profile page.

John W. Patrick's Articles: (13)

The strength of industrial cokes: Part 4. The influence of carbonizing conditions on the tensile strength

AbstractThe objective of this study was to ascertain if the observed differences in strength behaviour of blast-furnace and foundry cokes could be attributed to the different carbonizing conditions used in their production. Two coal blends, one being representative for blast-furnace coke production and the other for foundry coke production, were carbonized in a small-scale test oven using a wide range of heating conditions which included those used in the industrial production of the two types of coke. Coke tensile strengths were determined by the diametrical-compression test and a small-scale drum test was used to derive strength indices comparable to standard micum indices. The tensile strengths and material constants obtained by Weibull statistical analysis, when related to those drum-test indices which assess the resistance of coke to attrition and to corresponding data for equivalent commercial cokes, demonstrated that the cokes fell into two distinct sets according to the coal blend used. It was concluded that changes in coke strength caused by different carbonizing conditions could not account for the different strength behaviour of blast-furnace and foundry cokes. The alternative hypothesis that the nature of the coal blend is the predominant factor is supported by the correlations established for each of the coal blends.

The strength of industrial cokes. 5. Influence of coke breeze in a coal charge on tensile strength of coke

AbstractThe purpose of this study was to determine the influence of different proportions and different particle sizes of coke breeze in a coke-oven charge on the tensile strength of the coke. The diametrical-compression test was used to determine the tensile strength of the coke produced in a 10-t test oven and the results obtained were considered in relation to the composition of the oven charge, the coke micum indices and to parameters describing the coke texture. It was established that breeze additions caused measurable but nonsystematic changes in the coke tensile strength and that decreasing the breeze particle size generally increased the coke tensile strength. These changes could not however be directly related to changes observed in the density, porosity, pore-wall thickness or mean pore size of the cokes. The previously established relations between micum indices and the tensile strength of foundry cokes were also found to be inapplicable. The conclusion was drawn that the behaviour described is associated with some, at present unestablished, factor of the blend composition, one possibility being the relative proportions and compatibility of the ‘binder’ and inert material acting through their influence on those aspects of the coke microstructure which control the coke breakage.

Microscopic examination of polished coke surfaces etched by ion bombardment

AbstractThe purpose of this study was to assess the use of ion etching as a means of enhancing the more ordered features of the surface of polished coke sections so as to examine more closely details of the mosaic units identified in polarized-light microscopy. A series of 1000 °C vitrain cokes were examined by polarized-light and scanning-electron microscopy before and after etching of the surface by argon-ion bombardment. Using light microscopy, determinations were made of the anisotropic composition of the cokes and size of the mosaic units. From the scanning-electron microscopy a morphological description of the anisotropic type and a diametral sizing of the mosaic units were obtained. Ion etching of a polished coke surface is shown to be useful in producing a surface suitable for examination by the scanning-electron microscope. The results confirm that the units which constitute the mosaic anisotropy are in the form of distorted spheres, that the size of the units is directly related to coal rank, and that the flow-type anisotropy apparently results from the alignment and overlapping of the same basic units. The results also indicate that the maximum size of the individual units which make up the anisotropy is less than 2 μm.

The strength of industrial cokes. 7. Further studies of the influence of additives in a coke-oven charge on the tensile strength of coke

AbstractThe objective of this investigation was to determine if the previously established dependence of the tensile strength of coke on the breeze content and particle size of coke breeze in the coke-oven charge was applicable to different types of breeze additives when used in a size range similar to that of commercial practice. Using a small-scale oven to obtain the desired close control of the charge preparation and carbonization conditions, cokes were prepared from a Yorkshire strongly-caking coal blended with either coke-oven breeze, petroleum-coke breeze, or silica sand. The tensile strength of the cokes was determined by the diametral-compression test and some details of their porous structure were obtained from density measurements and mercury pressure porosimetry. The results confirm that the tensile strength of coke varies systematically with the coke-oven breeze content of the oven charge, and in the present case, for a breeze of the particle size range used in commercial practice the tensile strength is increased at low additions and then progressively reduced at higher levels of addition. Different sources of coke-oven breeze behave in a similar manner and appear to act as an inert filler material. On the other hand petroleum-coke breeze additions progressively increase the coke tensile strength, the additive being bonded into the walls of the coke matrix. The changes in tensile strength are accompanied by systematic variations in apparent density and in porosity.

Characterization of coal chars by Raman spectroscopy, X-ray diffraction and reflectance measurements

AbstractRaman spectroscopy is potentially a very useful technique for characterizing heterogeneous carbons and cokes. This paper describes an investigation of the relationships between Raman spectral parameters, optical reflectance measurements, and crystallite diameter, La, determined by X-ray diffraction measurements. It is shown that the Raman D (1360 cm−1) bandwidth correlates with La for cokes with heat treatment temperatures in the range 500–1900 °C, the bandwidth decreasing as the crystallite diameter increases. The X-ray diffraction and Raman measurements do not correlate with the reflectance measurements. These results are discussed in terms of the coke structure and they suggest that Raman spectroscopy and reflectance measurements are potentially useful for characterising differences in thermal history in heterogeneous char samples.

Main paperInfluence of pitch additions on coal carbonization: Coke strength and structural properties

AbstractThe influence of pitch addition to charges of single low-rank caking coals and to a blend of low- and high-rank coals was investigated using a small oven capable of producing dense, high-strength coke in amounts sufficient to permit measurement of strength and structural parameters. For the single-coal charges, changes in the carbon textural index induced by pitch addition were associated with corresponding changes in the coke microstrength. However, addition of any of the pitches studied resulted in reduced coke tensile strength, the reductions being greatest for those pitches which most markedly enhanced the coke textural index. Reductions in tensile strength were consistent with the observed changes in the pore structural parameters. The blended charge gave a low-porosity coke with low strength, implying that the coals were incompatible, lacking mutual fusibility. Pitch addition resulted in increased textural index and microstrength and reduced porosity but only small changes in tensile strength. For these charges it is considered that enhanced blend fusibility offsets the adverse influence of reduced porosity on coke tensile strength.

Short communicationOptical anisotropy in cokes from high-rank coals

AbstractSamples of cokes, obtained by carbonizing crushed coal to 1000 °C at 5 °C min−1, have been re-examined in an attempt to resolve why anisotropic textural components, all originally classified as flow-type, could be formed during the carbonization of high-rank coals of widely differing character by different formation routes. It was found that sub-division of this category of material into striated-flow, broad-flow and patterned anthracitic sub-groups permitted the clearer differentiation between cokes from high-rank coals according to their rank. Negligible fluidity and relatively little structural change appear to be involved in the formation of patterned-anthracitic components, the patterning reflecting variations of bedding layers in the coal. In contrast, both flow categories of component are formed from reactive coal constituents that exhibit some fluidity during carbonization. However, both components can be formed from the parent vitrinite either directly or via the intermediate formation of mosaic anisotropic components.

Full paperRapid hydropyrolysis studies on coal and maceral concentrates

AbstractThe primary devolatilization product distributions resulting from the rapid pyrolysis and hydropyrolysis of three coals and associated maceral concentrates were studied to assess the influence of coal and maceral type on reactivity and product formation. The influence of hydrogen on total product yield depended on both coal type and maceral group. In comparison with vitrinite and exinite concentrates, inertinite maceral concentrates showed high reactivity to hydrogen at high temperatures.

An accurate volumetric differential pressure method for the determination of hydrogen storage capacity at high pressures in carbon materials

AbstractWidely different hydrogen adsorption capacities have been reported for a variety of carbon materials which have attracted attention for hydrogen storage. This has led to doubts as to the validity of some of the claims and it has been suggested that one possible reason for the disparate hydrogen sorption capacities may lie in the inaccurate measurement of the hydrogen adsorbed. The aim of the work described in this paper was to make a contribution to this debate by developing a means and method of producing repeatable, accurate measurements of hydrogen sorption capacity in carbon materials. The apparatus developed is a volumetric differential pressure set-up operating at up to 10 MPa and the method has a conservative limit of detection of 0.1 wt% and an accuracy of ±0.05 wt%, using 1.0–2.5 g samples of the carbon materials studied. These included a carbon nanofiber sample and a series of activated carbons, the latter displaying a direct correlation between the BET effective surface area and the hydrogen sorption capacity of the materials. The amount of hydrogen adsorbed was less than 1 wt% for all the carbons examined.

Full paperCoal hydrogenation catalysis using industrial catalyst (MoO3NiO/Al2O3) ‘waste’

AbstractThis study is concerned with assessing a commercial MoO3NiO/Al2O3 (Akzo 153) catalyst which had been used in a coal-liquid upgrading process for 400 h, to promote low-severity coal hydrogenation. Such a reaction system is considered to be practically economic. A tubing bomb microreactor (25 cm3 capacity) was used for dissolution reactions of a low-rank British bituminous coal in an industrial recycle solvent under various conditions. Results show that this catalyst ‘waste’ exerts considerable influence on the coal hydrogenation reactions, although its activity is reduced, compared with a fresh sulfided catalyst of the same type. This research has also improved understanding of the catalysed coal hydrogenation mechanisms and has identified a potentially beneficial method of disposal of industrial catalyst wastes.

Full paperEffect of coal properties and porous structure on tensile strength of metallurgical coke

AbstractThe tensile strength of coke was studied to obtain a better understanding of coke strength and its relation to coal properties. The tensile strength was examined by considering coke as a porous material with two influential factors, namely, the matrix strength and the porous structure, which were estimated from the measured tensile strength and porosity. The coke carbon matrix was evaluated in the light of the structure of the coke carbon estimated using X-ray diffraction on the basis of the concept of graphitic and non-graphitic carbon. It was found that the coke matrix strength becomes stronger as the coke carbon structure approaches that of non-graphitic carbon. The porous structure was governed by the coking properties, in this case, the maximum fluidity and the swelling number. As regards the factors governing the coke porous structure, determined by means of image analysis and optical microscopy, it was demonstrated that a poor porous structure was associated with a wide pore size distribution caused mainly by a high proportion of the pores of length < 20 μm, and a rough surface of the pore periphery, which provides potential stress concentration points. The strength anisotropy, which is considered to affect the route of a crack path in lump coke, was also related to pore orientation and the quality of the porous structure.

Pteris umbrosa R. Br. as an arsenic hyperaccumulator: accumulation, partitioning and comparison with the established As hyperaccumulator Pteris vittata

AbstractThe capacity of the Australian native fern Pteris umbrosa to function as an arsenic (As) hyperaccumulator (shoot:soil As concentration >1) was examined by growing plants under glasshouse conditions in an inert medium supplemented with As. Arsenic preferentially accumulated in the fronds, a trait of a hyperaccumulator. The As concentration of fronds decreased with age, being particularly high in the croziers and low in the senesced fronds. Below ground, rhizomes accumulated more As than adventitious roots. Uptake from a range of solution concentrations followed Michaelis Menten kinetics up to a soil solution As concentration of 400 mg l−1. The Km for As uptake by roots suggested the operation of a low-affinity carrier. The predicted Nernst membrane potential indicated that uptake was against the electrochemical gradient of As. At 600 mg l−1, the rate of As uptake increased and phytotoxic effects were indicated by a significant decline in biomass. Arsenic uptake and translocation in P. umbrosa and Pteris vittata were similar at low exposure to As. At higher exposure, As uptake and translocation by P. vittata increased more than in P. umbrosa. The growth rate of both ferns was similar, whereas the biomass distribution was not, with P. vittata having a much larger root mass. This suggests that As uptake by P. umbrosa roots was very efficient and may be improved by stimulating root growth to enhance its potential.

ReviewMolecular regulation of seed and fruit set

Seed and fruit set are established during and soon after fertilization and determine seed and fruit number, their final size and, hence, yield potential. These processes are highly sensitive to biotic and abiotic stresses, which often lead to seed and fruit abortion. Here, we review the regulation of assimilate partitioning, including the potential roles of recently identified sucrose efflux transporters in seed and fruit set and examine the similarities of sucrose import and hydrolysis for both pollen and ovary sinks, and similar causes of abortion. We also discuss the molecular origins of parthenocarpy and the central roles of auxins and gibberellins in fruit set. The recently completed strawberry (Fragaria vesca) and tomato (Solanum lycopersicum) genomes have added to the existing crop databases, and new models are starting to be used in fruit and seed set studies.

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