Yallourn Brown Coal Research Articles

Reactivity and Performance of Alkali-Activated Yallourn Brown Coal Ash

Reactivity and Performance of Alkali-Activated Yallourn Brown Coal Ash

Yallourn brown coal – The effect of drying conditions on its VOC emissions

Thermal drying of Victorian brown coals is typically accompanied by a characteristic “odour” associated with their emission of Volatile Organic Compounds (VOCs). Evaluating the health implications of VOC emissions from coal mine fires and large scale coal mining or drying operations requires the yield and composition of these chemicals to be investigated. This paper focuses on the hydrophobic compounds released during the mild (40°C–105°C) thermal treatment of Yallourn coal utilising various purge and trap systems coupled with Gas Chromatography Mass Spectrometry (GC/MS). These VOCs comprise a complex mixture dominated by ppm yields of isoprenoids with trace (ppb) amounts of BTEX and aldehydes and ketones. No evidence was found to suggest these isoprenoids would cause health and safety concerns at the ultra-low levels predicted in ambient air samples. Emissions under inert and oxidising atmospheres both showed increasing VOC yields in response to higher temperatures and the amount of water removed. The presence of inherent “free” or bulk water was found to markedly enhance VOC release. The use of oxidative purge gas during brown coal drying was only effective in producing higher yields of oxidative products such as aldehydes once bulk water was removed. The predominant VOCs released during drying were found to be resin derived hemi and monoterpenes which would account for the typical odour associated with drying brown coals.

Ignitability and Combustibility of Yallourn Pyrolysis Char Blended with Pulverized Coal Injection Coal under Simulated Blast Furnace Conditions

Pulverized coal injection (PCI) is a widely used blast furnace technology aimed at reducing costs and increasing productivity. The prospect of blending PCI coal with a lower cost char, derived from Yallourn brown coal, is evaluated in this study by means of thermogravimetric analysis (TGA), flat-flame burner reactor, and drop-tube furnace experiments at four different blending ratios as well as computational fluid dynamics (CFD) modeling. Yallourn char has desirable properties compared to PCI coal, including a lower ash content and a higher heating value, although the reactivity is lower and the ignition temperature is higher. Because the combustion behavior of a blend is not always easily predicable based on the performance of the individual parent fuels, two Yallourn char samples (YC-1 and YC-2) are analyzed after blending with PCI coal at four ratios. According to the particle ignition time, a maximum of 40 wt % is allowable for YC-1 char which is comparably reactive with the commercial PCI coal. Howev...

Mechanisms Underpinning the Mobilization of Iron and Magnesium Cations from Victorian Brown Coal Fly Ash

This paper reported the leaching of Yallourn brown coal fly ash uniquely rich in magnesioferrite (MgFe2O4) using hydrochloric acid, by varying acid concentration, liquid-to-solid (L/S) ratio, temperature, and time, to understand the mechanisms underpinning the extraction of iron and magnesium. Results indicate that Yallourn fly ash is composed of a densely packed, crystalline ash matrix, mainly in the form of MgFe2O4 and maghemite (γ-Fe2O3). Thermal cleaving at 100 °C and above liberates embedded octahedrally coordinated Fe3+, a controlling step for the leaching process. Increments from 100 to 200 °C did little to enhance extraction of Fe and Mg in single-stage leaching. Except at 70 °C, the thermal decomposition for the elution of both metals was complete within 1 min, while increasing the L/S ratio and acid concentration had negligible influence. The application of two-stage leaching gave protons a larger driving force to access embedded unreacted species. Subsequently, the extraction yields of both Fe ...

05/00953 Production of carbon nanotubes from coal

Time profiles of weight change of coal samples and the evolution of low molecular weight gases (H2, CH4, CO and CO2) in both steam gasification and pyrolysis of Yallourn brown coal and Taiheiyo subbituminous coal were measured using a thermobalance reactor with a micro GC and a mass spectrometer, in order to examine the reaction mechanism of steam gasification with rapid heating (100 K s−1). It was found that, in the case of slow heating, steam reacted with metaplast and promoted the evolution of tar above 623 K and that a water shift reaction took place above 873 K. Steam gasification of produced char occurred above 1023 K, increasing the evolution of CO, CO2 and H2. When the heating rate was high, steam reforming of volatile matter and steam gasification of metaplast took place parallel to metaplast formation and condensation. The char produced by pyrolysis was almost completely gasified and converted into H2 and CO2 by steam. The chemical energy of coal was mainly converted into hydrogen energy and the gasification efficiency was slightly increased by rapid heating (i.e. 100 K s−1).

Steam gasification characteristics of coal with rapid heating

Time profiles of weight change of coal samples and the evolution of low molecular weight gases (H 2, CH 4, CO and CO 2) in both steam gasification and pyrolysis of Yallourn brown coal and Taiheiyo subbituminous coal were measured using a thermobalance reactor with a micro GC and a mass spectrometer, in order to examine the reaction mechanism of steam gasification with rapid heating (100 K s −1). It was found that, in the case of slow heating, steam reacted with metaplast and promoted the evolution of tar above 623 K and that a water shift reaction took place above 873 K. Steam gasification of produced char occurred above 1023 K, increasing the evolution of CO, CO 2 and H 2. When the heating rate was high, steam reforming of volatile matter and steam gasification of metaplast took place parallel to metaplast formation and condensation. The char produced by pyrolysis was almost completely gasified and converted into H 2 and CO 2 by steam. The chemical energy of coal was mainly converted into hydrogen energy and the gasification efficiency was slightly increased by rapid heating (i.e. 100 K s −1).

Prediction of coal liquefaction reactivity by solid state 13C NMR spectral data

A method for the deconvolution of 13C NMR spectra of coals has been developed by using coal-like model compounds and various lithotypes separated from Yallourn brown coal which is rich in various types of oxygen-functional groups. The spectrum of coal was resolved into 24 peaks which were classified into nine types of carbon-functional group. This analytical method can be applied to all ranks of coal from lignite to anthracite. In addition, the liquefaction data of seven kinds of coal collected from five different countries were obtained by the operation of 1 t/d process support unit and 150 t/d pilot plant NEDOL process liquefaction plants. A good correlation was obtained for every reaction product between structural data derived from solid state 13C NMR spectra and liquefaction data of coals. This means that the yields of liquefaction products could be predicted from 13C NMR spectral data of coal.

Estimation of Size and Shape of Pores in Moist Coal Utilizing Sorbed Water as a Molecular Probe

This work has been undertaken aiming to estimate the size of pores in moist coals on the basis of the nuclear magnetic resonance relaxation characteristics of water sorbed in the pores as the molecular probe. Raw Yallourn brown coal (water content; 1.46 kg-water/kg-daf coal) and Beulah Zap lignite (0.53) were employed as the raw materials and were partially or completely dried at 303 K. Samples with known water contents were subjected to 1H NMR analysis taking a Carr-Purcel/Meiboom-Gill (CPMG) pulse sequence. The results of the analysis revealed that the initial amplitude of the CPMG signal corresponds quantitatively to the total amount of ‘mobile‘ proton. It was found that there are three components with different transverse relaxation times (T2), that are attributed to free water, pore water (freezable bound water and nonfreezable water), and mobile coal hydroxyls. The relaxation characteristics of the water components were further analyzed on the basis of a theory that relates the dimension of pore to ...

Co-liquefaction of Micro Algae with Coal Using Coal Liquefaction Catalysts

Co-liquefaction of micro algae (Chlorella, Spirulina, and Littorale) with coal (Australian Yallourn brown coal and Illinois No. 6 coal) was carried out under pressurized H2 in 1-methylnaphthalene at 350−400 °C for 60 min with various catalysts. Co-liquefaction of Chlorella with Yallourn coal was successfully achieved with excess sulfur to iron (S/Fe = 4), where sufficient amount of Fe1-xS, which is believed to be the active species in the coal liquefaction, was produced. The conversion and the yield of the hexane-soluble fraction were close to the values calculated from the additivity of the product yields of the respective homo-reactions. In the reaction with a one-to-one mixture of Chlorella and Yallourn coal, 99.8% of conversion and 65.5% of hexane-soluble fraction were obtained at 400 °C with Fe(CO)5 at S/Fe = 4. When Littorale and Spirulina were used as micro algae, a similar tendency was observed with the iron catalyst. On the other hand, in the co-liquefaction with Illinois No. 6 coal, which is known to contain a large amount of sulfur in the form of catalytically active pyrite, the oil yield in the co-liquefaction was close to the additivity of the respective reaction with Fe(CO)5−S, even at S/Fe = 2. Ru3(CO)12 was also effective for the co-liquefaction of micro algae with coal.

Mobilization of the Hydroxyls in a Brown Coal with Solvent-Induced Swelling Evaluated by Pulsed 1H NMR

The amount of hydroxylic hydrogen mobilized with the solvent-induced swelling of a brown coal was measured using a pulsed 1H NMR technique. Yallourn brown coal (YL), and deuterated YL (YL-d), prepared by selectively deuterating all the hydroxyls in YL, were swollen in binary solvents, including different pyridine-d5/benzene-d6 and dimethyl sulfoxide(DMSO)-d6/benzene-d6 mixtures, at 303 K. The volumetric swelling ratio (Q) and the amount of mobile hydrogen were measured as a function of the composition of the solvent. The amount of hydroxylic hydrogen remaining immobile, fIM(OH), was also determined experimentally by comparing the amounts of mobile hydrogen in YL and YL-d. The fIM(OH) of YL in DMSO−benzene mixtures was found to be smaller than that in pyridine−benzene mixtures over the entire range of Q from 1 to 3.5, demonstrating that DMSO reduces the hydrogen bonding associations between coal macromolecules more extensively than pyridine does for the swelling with equivalent Q. The effects of these pola...

99/00053 Kinetics of Yallourn brown coal devolatilization at elevated pressure in an entrained flow reactor

99/00053 Kinetics of Yallourn brown coal devolatilization at elevated pressure in an entrained flow reactor

Rapid devolatilisation of Yallourn brown coal at high pressures and temperatures

A pressurised drop-tube furnace was used to study the devolatilisation behaviour of Yallourn brown coal. Coal particles of 37–53 μm size were devolatilised at pressures of 100, 500 and 1000 kPa. The experiments were carried out at temperatures of 873, 1073 and 1273 K. Residence times were varied from 0.02 to 3 s. Weight loss was calculated based on ash as a tracer. The maximum weight loss due to devolatilisation is temperature and pressure dependent. At a particular residence time and pressure, the weight loss increases with an increase in devolatilisation temperature. Increasing the pressure not only increases the residence time required to achieve a given level of weight loss, but also reduces the total weight loss attainable at a particular temperature. Weight loss due to devolatilisation was fitted by a 2-stage first-order kinetic expression. The calculated kinetic parameters are considerably lower than the reported parameters for lignites and bituminous coals. It appears that initial devolatilisation of Yallourn brown coal is mainly dominated by very low activation energy. Variation of activation energy with the level of devolatilisation was observed. This variation could be partially due to the presence of active sites in the char with different characteristic reactivities.

Cyclopenta-fused polycyclic aromatic hydrocarbons from brown coal pyrolysis

To examine certain aspects of coal tar composition, we have pyrolyzed acid-washed Yallourn brown coal under nitrogen at temperatures of 600 to 1000°C in a fluidized-bed reactor. Analysis of the product tar by reverse-phase high-performance liquid chromatography with diode-array ultraviolet-visible absorption detection reveals that the tars are composed of a large number of polycyclic aromatic compounds, many of which are polycyclic aromatic hydrocarbons (PAH) with peripherally fused cyclopenta rings (CP-PAH). Among PAH, CP-PAH are of particular interest because of their proneness to oxidation in the en vironment, their relatively high biological activity, and their postulated role in soot formation. Of the 10 CP-PAH identified in our tar samples, 4 of the most abundant are acenaphthylene (C12H8), acephenanthrylene and aceanthrylene (C16H10), and cyclopental [cd]pyrene (C18H10)—all of which have been detected previously in products of coal pyrolysis and/or combustion. The recent synthesis of several new CP-PAH reference standards, however, has enabled us to also identify, in the brown coal tars, six additional CP-PAH-cyclopent[hi]acephenanthrylene and cyclopenta[cd]fluoran thene (C18H10), dicyclopenta[cd, mn]pyrene and dicyclopental[cd, jk]pyrene (C20H10), benzo[ghi]cyclopenta[cd]perylene (C24H12), and cyclopenta[bc]coronene (C26H12)—none of which has ever before been identified in coal products. The mass fractions of individual CP-PAH span a range of four orders of magnitude—from 0.000062 for cyclopenta[bc]coronene to 0.265 for acenaphthylene in the 1000°C tar smaple. Accounting for approximately one-third of the mass of the tar produced at 1000°C, the CP-PAH yields show a monotonic increase with pyrolysis temperature—confirming that the CP-PAH are not primary products of coal devolatilization but instead result from secondary pyrolytic reactions in the gas phase. Possible reaction mechanisms are explored.

Flow Microcalorimetric Study of Methanol Adsorption from n-Hexane on Coals

The heat evolved by mixing of methanol and a coal was measured by flow microcalorimetry (FMC) to investigate interactions between coal and methanol. Such interactions were classified into weak and strong adsorption. Two adsorption methods were used: continuous flow for measuring combined weak and strong adsorption, and pulse injection to distinguish strong adsorption. Akabira bituminous coal and Yallourn brown coal, having different oxygen contents, were used as adsorbents. Experimental results achieved by the continuous flow method show that both amount and heat of methanol adsorption (2 g of methanol/L in n-hexane) depends on the structure of coal. Methanol uptakes were also measured, off-line, by immersing the coals in methanol−hexane solutions of different concentrations and comparing methanol concentrations in n-hexane before and after adsorption. Methanol adsorption isotherms so obtained have the same shape and the total uptakes of methanol adsorption are almost the same in spite of different coal ...

97/04400 Devolatilization of Yallourn (Australia) brown coal at elevated pressure in an entrained flow reactor: Mathews, J. F. DGMK Tagungsber., 1997, 9703, (Proceedings ICCS '97, Volume 2), 629–632

97/04400 Devolatilization of Yallourn (Australia) brown coal at elevated pressure in an entrained flow reactor: Mathews, J. F. DGMK Tagungsber., 1997, 9703, (Proceedings ICCS '97, Volume 2), 629–632

97/04631 Characteristics of chars produced from devolatilization of Yallourn brown coal at elevated pressure: Yeasmin, H. et al. DGMK Tagungsber., 1997, 9703, (Proceedings ICCS '97, Volume 2), 689–692

97/04631 Characteristics of chars produced from devolatilization of Yallourn brown coal at elevated pressure: Yeasmin, H. et al. DGMK Tagungsber., 1997, 9703, (Proceedings ICCS '97, Volume 2), 689–692

89.イオン交換により担持させた鉄-ニッケル二元触媒によるヤルーン炭の液化反応

89.イオン交換により担持させた鉄-ニッケル二元触媒によるヤルーン炭の液化反応

Proton magnetic resonance thermal analysis of a brown coal: effects of ion-exchanged metals

Four versions of a Yallourn brown coal, each distinguished by the form of its carboxyl groups (acidic or cation-exchanged with Na, Ca or Ba), were subjected to proton magnetic resonance thermal analysis from 25 to 575°C. Analysis of the profiles of two second-moment parameters, calculated from the transverse relaxation signals of each coal, indicates the following: (1) Upon heating, cation-exchanged coals attain a lower extent of fusion (i.e. they are more rigid structures) than the acid-form coal—the two divalent cations Ba and Ca having a greater effect on fusion reduction than the monovalent cation Na. (2) The matrix densities of the coals follow the order: acid-form < Na-form < Ba-form = Ca-form. The results provide insight into earlier experimental observations of the cation-induced hindrance of solvent penetration into coals and of the suppression of plastic behaviour and tar production during rapid pyrolysis.

The effects of pyrolysis temperature and ion-exchanged metals on the composition of brown coal tars produced in a fluidized-bed reactor

In order to investigate the effects of temperature and ion-exchanged metals on brown coal tar composition, we have pyrolyzed raw, acid-washed, sodium-exchanged, and calcium-exchanged Yallourn brown coal in a fluidized-bed reactor at temperatures of 600–1000°C. Tar yiels adhere to the order: acid-washed > raw > Na-form > Ca-form-reflecting the cations' ability to bring about a more rigid and compact coal structure, which hinders the escape of large tar molecules evolved during coal develatilization. Analysis of the tars by high-pressure liquid chromatography with ultraviolet-visible diode-array detection reveals that the tars are composed mainly of aliphatic species at the lowest pyrolysis temperatures. An increase in pyrolysis temperature brings about a decrease in the aliphatic components and an increase in the aromatic portion of the tar. At low temperatures, the aromatic portion of the tar is composed of a large number of mostly substituted aromatic species. The distribution of products narrows, however, as pyrolysis temperature is raised and dealkylation and decarbonylation reactions take place. Concurrently, the contribution from ring-nitrogen-containing aromatics falls, in accordance with their lower relative thermal stability. At the highest pyrolysis temperatures, tar composition is dominated by unsubstituted polycyclic aromatic hydrocarbons. Compared to temperature, sodium and calcium exhibit only modest effects on tar composition—the primary one being the suppression of the yield of aromatics containing ring nitrogen. At the lower pyrolysis temperatures, the tars from the Ca-form coal are richer in aliphatic content than the tars from the other coals, suggesting that the aliphatic products of devolatilization are less susceptible than the aromatic products to the cation-induced hindrance of tar molecule escape during coal pyrolysis. The effects of the metals become less pronounced at higher pyrolysis temperatures, however, where thermal factors govern the product distribution.

Application of microscopy to the investigation of brown coal pyrolysis

To examine the influence of calcium on the mechanisms of brown coal pyrolysis and gasification, the morphology of chars from raw and calcium-exchanged Yallourn brown coal was analysed. The chars were obtained by slow pyrolysis in a thermo gravimetric analyser and rapid pyrolysis in fluidized bed reactors operating at atmospheric pressure and at 1.1 MPa. They were examined by optical microscopy to determine reflectance and the percentage of particles that had become plastic during pyrolysis. In addition to confirming calcium's inhibiting effect on tar yield, the results from the rapid pyrolysis experiments show that in the presence of calcium, char reflectivity decreases, char H/C ratio increases, and the proportion of particles going through a plastic stage decreases. Calcium's inhibition of plasticity development is augmented by high pressure in the fluidized bed reactor. The effects appear to be attributable to the action of carboxylate calcium as a cross-linking agent, leading to the formation of a tighter char structure which traps the organic material that would otherwise be liberated as tar. The presence of Ca also increases the H/C ratio of the chars produced by slow pyrolysis, but the mechanism of pyrolysis differs, since in slow pyrolysis none of the particles showed evidence of plasticity. In slow pyrolysis, calcium's influence on char reflectivity depends on the holding temperature, since temperature determines the extents of both coal devolatilization and catalytic transformations. The roles of calcium in these processes and their influence on optical anisotropy and reflectance are discussed.