Pyrolysis of Coal

The paper presents a review of relevant literature on coal pyrolysis.Pyrolysis, as a process technology, has received considerable attention from many researchers because it is an important intermediate stage in coal conversion.Reactions parameters as the temperature, pressure, coal particle size, heating rate, soak time, type of reactor, etc. determine the total carbon conversion and the transport of volatiles and therebythe product distribution. Part of the possible environmental pollutants could be removed by optimising the pyrolysis conditions. Therefore, this process will be subsequently interesting for coal utilization in the futur

ASSISTED DEVELOPMENT OF MESOPHASE PITCH WITH DISPERSED GRAPHENE AND ITS RESULTING CARBON FIBERS

The efficacy of dispersed reduced graphene oxide (rGO) as a nucleation site for the growth of mesophase in an isotropic pitch was investigated and quantified in this study. Concentrations of rGO were systematically tested in an isotropic petroleum and coal-tar pitch during thermal treatments and compared to pitch without rGO. The mesophase content of each thermally treated pitch was quantified by polarized light point counting. Further characterization of softening temperature and insolubles were quantified. Additionally, the pitches with and without rGO were melt spun, graphitized, and tensile tested to determine the effects of rGO on graphitized fiber mechanical properties and fiber morphology

Piroliza ugljena

The paper presents a review of relevant literature on coal pyrolysis. Pyrolysis, as a process technology, has received considerable attention from many researchers because it is an important intermediate stage in coal conversion. Reactions parameters as the temperature, pressure, coal particle size, heating rate, soak time, type of reactor, etc. determine the total carbon conversion and the transport of volatiles and thereby the product distribution. Part of the possible environmental pollutants could be removed by optimising the pyrolysis conditions. Therefore, this process will be subsequently interesting for coal utilization in the future.Neovisno o tome da li se ugljen rabi za proizvodnju energije, ugljičnih materijala ili kemikalija, piroliza je početni korak procesa njegove konverzije. S obzirom na važnost i značenje još uvijek je predmetom brojnih istraživanja. Piroliza je proces zagrijavanja ugljena bez pristupa zraka kojim se dobivaju razni čvrsti, tekući i plinoviti produkti. Iako prema ovoj osnovnoj definiciji piroliza predstavlja jednostavan proces, u praksi on je složen od brojnih kemijskih reakcija i fizikalnih promjena koje opisuju razni mehanizmi. Za bolje razumijevanje mogućih reakcija i mehanizama u radu je ukazano na povezanost strukture ugljena i pirolize. Izdvojen je mehanizam pirolize najbliži stvarnim promjenama u strukturi (maceralima) ugljena pod utjecajem topline. Na dobivanje produkata primarnim i sekundarnim reakcijama utječu brojni faktori (temperatura, tlak, atmosfera, brzina i vrijeme zagrijavanja, vrsta ugljena, i sl.). Temperatura se izdvaja kao najvažniji faktor, a koks kao najčešće glavni produkt pirolize. Ukazano je na povezanost produkata karbonizacije pri niskim (400-750 °C) i visokim (750-1100 °C) temperaturama s reakcijama odgovornim za njihovo dobivanje i uporabu. Kao složena smjesa organskih i anorganskih tvari, ugljen može biti izvor brojnih onečišćivača okoliša. Optimiranjem procesnih parametara moguće je utjecati na emisiju štetnih tvari (naročito anorganskih elemenata u tragovima i spojeva sumpora i dušika) odnosno na smanjenje njihovog sadržaja u produktima pirolize

Investigation on the structure of carbonized pitch and calcined coke-carbonized pitch interface in carbon anodes by etching

A novel, simple, quick, and economic method has been developed to etch samples for characterizing the structural aspects of carbonized pitch alone and in baked anodes. Hot air is used to etch the polished carbonized pitch surface for creating its topography; followed by the characterization of the structure using scanning electron microscope. Hot air preferentially etches the carbonized pitch, which make the differentiation of carbonized pitch from the calcined coke particles possible in baked anode. After etching, lamellar parallel cracks are created and fine granular mosaics are observed on the surfaces of carbonized pitch. The structural composition in baked anode differs visibly from the pure carbonized pitch baked under the same conditions. This may be due to the effect of fine coke particles in anode on the formation of structure during baking. The etching technique permits the determination of the internal structure of carbonized pitch and its interface with coke in anode

Low shear rheological behaviour of two-phase mesophase pitch

The low shear rate rheology of two phase mesophase pitches derived from coal tar pitch has been investigated. Particulate quinoline insolubles (QI) stabilised the mesophase spheres against coalescence. Viscosity measurements over the range 10–106 Pa s were made at appropriate temperature ranges. Increasing shear thinning behaviour was evident with increasing mesophase content. At low mesophase contents the dominant effect on the near Newtonian viscosity was temperature but at higher contents it was the shear rate; temperature dependence declined to near zero. The data indicated that agglomeration could be occurring at intermediate mesophase volume fractions, 0.2–0.3. The Krieger– Dougherty function and its emulsion analogue indicated that in this region the mesophase pitch emulsions actually behaved like ‘hard’ sphere systems and the effective volume fraction was estimated as a function of shear rate illustrating the change in extent of agglomeration. At the higher volume fractions approaching the maximum packing fraction, which could only be measured at higher temperatures, the shear thinning behaviour changed in character and it is considered that this is possibly due to shear induced deformation and breakup of dispersed drops in the shear field.South African Research Chairs Initiative of the Department of Science and Technology (DST) and the National Research Foundation (NRF).http://www.elsevier.com/locate/carbon2016-02-28hb201

Study of the early stages of carbonisation of some pitch materials of different composition

The formation and development of mesophase from different pitches under carbonisation conditions was investigated. Members of the pyrolysis series were prepared from four pitches. A temperature range between 380 and 500°C was used to follow mesophase development for each pitch. As-received pitches and their green cokes were characterised by thermomechanical analysis (glass transition temperature and softening point temperature), elemental analysis, Fourier transform infrared spectroscopy, thermogravimetry or differential thermogravimetry, and optical microscopy (mesophase content). Additional data about the evolution of different volatile products and about possible chemical reactions occurring during thermal decomposition were obtained from thermogravimetric mass spectrometric analysis. The effect of heating rate on the behaviour and carbon yield was also studied. The results showed that the two anthracene oil pitches do not develop mesophase, whereas the medium-temperature and high-temperature pitches do. However, their textures are completely different. The medium-temperature pitch shows an improvement in texture from the mosaic to the coarse domain at 500°C, whereas the high-temperature pitch shows flow domains. It was further shown that the process of preparing mesophase, i.e. the heat-treatment process, increases the aromaticity and carbon yield. Thermogravimetric mass spectrometric analysis showed that the dominant reaction for all the pitches is the condensation reaction, which is accompanied by the evolution of H2 and CO. The heating rate affects the behaviour of the pyrolysing pitches in that a lower heating rate lowers the carbon yield. This study gave insight into the influence of the nature and composition of the precursor on the formation of mesophase.Dissertation (MSc)--University of Pretoria, 2009.Chemistryunrestricte