Associate Professor John Lucas

© 2016 Elsevier Ltd.In this paper, process simulation of a near-zero-carbon-emission power plant using CO2 as the renewable energy storage medium was carried out. Liquid fuels that can be burned either in boilers or compression ignition engines to generate electricity have been the target products. The CO2 and H2O produced from combustion are recirculated back to the synthesis units, thus forming a closed cycle of "renewable energy (unstable energy supply) + CO2 + H2O ¿ liquid fuels ¿ electricity (stable supply)". This novel closed loop energy storage process integrated with a 670 MW supercritical power plant was analyzed using the Aspen Plus software package. Methanol was selected as the targeted liquid fuel through three major synthesis routes: CO + H2, CO2 + H2 and CO2 + H2O, in which CO and H2 came from the electrolysis of CO2 and H2O. The performances of the three methanol synthesis routes were thermodynamically analyzed. The results show that the optimal methanol synthesis route is the direct conversion of CO2 and H2O through electrocatalysis when CO2 conversion is above 42%, while when CO2 conversion is below 42% the best choice turned out to be the CO hydrogenation. The direct conversion of (CO2 + H2O) using electrocatalysis method was adopted as the liquid fuel synthesis route for the near-zero-carbon-emission power plant. The overall CO2 emission from the near-zero-carbon-emission power plant is 44.13 kg/MWh accounting for just 6.45% of the advanced coal fired power plant.

© 2016 American Chemical Society.The thermoplastic development of an Australian coking coal was investigated by linking thermal swelling with changes in molecular weight of its pyrolysis products. Coal thermal swelling was investigated together with volatiles evolution and characterization of generated volatiles (including volatile tar and light gases). The molecular weight distributions of coal and its solvent extracts were measured by using laser desorption/ionization time of flight mass spectroscopy (LDI-TOF-MS). Solvent extraction (by acetone and tetrahydrofuran (THF)) was initially used on the raw coal to aid interpretation of thermoswelling by volumetric expansion measurements. The removal of ~2% solvent-soluble matter from the raw coal (the mobile phase) reduced its swelling extent during heating by up to 22% (from 86% down to 68% and 64% for acetone- and THF-residues, respectively). Volatile release after solvent treatment remained unaffected. This suggested that the majority of the coals swelling behavior could be attributed to the formation of heat-generated liquid matter (the Metaplast) during pyrolysis. Broad molecular weight changes were found in the solvent extractable component (metaplastic material extracted by acetone and THF) of the semicoke. Prior to softening (350 °C), the extractable components were composed of molecules mainly <500 Da. The upper limit in molecular weight distribution of solvent extracts increased significantly to 1800 Da at the onset of swelling (400-450 °C) and decreased back to ~500 Da at the end of swelling (500 °C). The spectra showed that the volatile tar and acetone extract (the light solvent extract) consisted of similar repeating structures separated 12-14 Da apart. As the treatment temperature increased, the molecular weight distribution of volatile tar increased in molecular mass, approaching that of the acetone extract distribution (~600 Da). The THF extract molecular weight distribution was a mixture of 12-14 and 24 Da repeating units which only became apparent at molecular weight above 600 Da. The LDI-TOF-MS analysis of the solid coal showed that it contained a distribution of molecular structures centered at 2000 Da and spanning between 500 and 7000 Da. This raw coal spectrum also contained multiple repeating mass lines every 24 Da apart. Overall, these results suggested that the coal consisted of complicated structures which subsequently degraded into smaller fragments capable of forming a complex intermediate liquid phase and a distribution of lighter volatile tar species.

© 2014 Elsevier Ltd. All rights reserved.In this research, coal combustion behavior across the regions of blowpipe, tuyere, and raceway of blast furnace are numerically examined. Three different lance configurations, including a single lance, a double air-cooled coaxial lance, and an oxy-coal lance with different oxygen enrichment patterns, are taken into consideration. The coal combustion efficiency by the double lance injection is 5.1% higher than that by single lance injection. From the calculated temperature by the oxy-coal lance, coal ignition is retarded due to the cooling effect of enriched oxygen flowing through the lance annulus, resulting in the moderation of pressure loss within the raceway. Most importantly, the enriched oxygen becomes the combustion enhancer in the downstream of coal plume after ignition is triggered. Consequently, the coal burnout under the oxy-coal lance injection is comparative to that under the double air-cooled lance injection. The performance of blast furnace may be improved with the advantages provided by the oxy-coal lance injection. Compared with the single lance injection, coal trajectories under the oxy-coal lance injection are closer to the tuyere exit due to the higher inertia force of coal particles against hot blast. This should be taken into account for the designs of the oxy-coal lance.

© 2015 Elsevier Ltd. All rights reserved.Dynamic measurements of physical, chemical and thermal changes in the transformation of coal maceral concentrates were made during heating at a rate of 10°C/min to 1000°C. The endothermic and exothermic processes were identified by measurements of apparent specific heat while the fluidity was indicated by the estimated thermal conductivity. Measurements of swelling and bed permeability were made, with continuous quantitative elemental analysis of gases and tars as they evolved. Data for two coal concentrates of high and moderate vitrinite indicate that the same reactions and events are occurring for the two samples, but to a greater extent for the high vitrinite sample. The research has noted the significance of evolved tars in the early events, being the lowest temperature event identified, with rapid tar evolution prior to the onset of swelling associated with permeability change. Further tar release and gas evolution is associated with a rapid swelling event, this event being substantially greater for the high vitrinite sample. The data has also quantified contraction at higher temperatures following swelling which is associated with the release of hydrogen containing gases. Evolved tars from the high vitrinite sample showed elevated H/C ratio indicating that vitrinite tars appear to be more aliphatic than those evolved from inertinite. A comparison of measured swelling with estimated volumetric flow rate of the volatiles has indicated that thermo-expansion of coal utilised up to 21% of the volatiles to drive bubble growth. This utilisation rate varied significantly across the plastic temperature range.

© 2015 American Chemical Society.A fundamental study was undertaken to characterize the changes in solvent-extracted matter formed during the thermoplastic phase of coking. Coal samples were heated to fixed temperatures within the pyrolytic plastic range of 400-500 °C, and the volatile material was extracted in a two-stage extraction with acetone (light extract) and then tetrahydrofuran (THF heavy extract). The extracted material was analyzed using laser desorption ionization (time-of flight) mass spectrometry (LDI-TOF-MS). The LDI-TOF-MS results showed that three extracted fractions could be broadly classified here as overlapping molecular weight ranges as volatile tars (200-450 Da), light acetone-soluble extract (250-500 Da), and heavy THF-soluble extract (300-1200 Da). A further class of compounds was identified from THF extraction of the raw coal in the range of 600-2500 Da that required higher laser powers to ionize and was not observed in the thermally generated samples. Negligible changes were observed in the composition of the acetone-soluble extracts with temperature, while the THF-soluble extract showed smaller proportions of larger molecules with higher treatment temperatures. It was observed that each molecular weight spectrum showed repeating structural units forming peaks every 12-14 Da (homologous series), with distributions of species around each peak. The volatile tar and acetone-soluble material shared common repeating structures also evident in the raw coal extract. This suggested that the material in this fraction was thermally stable over the analyzed temperature range. The repeating features of the THF-soluble extract species appeared to be structurally different. Overall, this work has indicated that development of extractable matter expected to be associated with fluidity during coking and subsequent resolidification relies on <1000 Da compounds. The results showed that >600 Da compounds are thermally sensitive. Compounds with molecular weights of <450 Da may be removed during coking, possibly as a vapor, resulting in a reduction in fluidity. There has been speculation that the thermally stable (acetone-soluble) material identified in both raw coal extract and those from thermally treated samples may be capable of undergoing a phase change to initiate plastic deformation.

© 2014 Elsevier B.V. All rights reserved.Solvent extraction and oxidation of coal under mild conditions can assist in understanding of coal chemical structure. It can also offer a potential for conversion of coal into useful chemicals, allowing more efficient use of coal resources. In this study, a Chinese lignite was extracted by different solvents including CS2, ethanol, and acetone. The composition of the extracts was analyzed by GC-MS method. It was found that the CS2 extracts contained high amounts of aliphatic hydrocarbon. The ethanol and acetone extracts mainly contained oxygen-containing compounds. The effects of reaction temperature and residence time on coal oxidation and composition of extract residueswere also investigated. The results showed that lignite was readily oxidized in H2O2 aqueous solution at temperatures above 40 °C, and the oxidation behavior (oxidation rate, product distribution and yields) was strongly temperature dependent. Oxidation of extract residues in H2O2 solution was carried out at different temperatures. Water soluble products of oxidation were analyzed using the GC-MS. Aliphatic hydrocarbons were present in all oxidation steps. The relative content of esters in all oxidation stepswas also high. The chemical structure changes of coal, the extract residues, and the oxidation residueswere studied using FTIR technique. The results indicated that the extract residues had lower intensity of aliphatic hydrogen compared to raw coal. The aromatic carbon concentration remained relatively unchanged when oxidized at temperatures below 30 °C, then decreased slightly with increasing the oxidation temperature.

Coke oven gas cleaning is an important issue in China, where it can be a source of liquefied natural gas (LNG) through the methanation process. In this study, char-supported sorbents were prepared by loading iron, cerium, and molybdenum into a Chinese lignite through co-precipitation, and the sorbents were used for dry desulfurization of coke oven gases. Desulfurization efficiency of the sorbents was examined using a fixed-bed reactor in a temperature range of 473-673 K using a simulated coke oven gas. A gas chromatograph equipped with both a flame photometric detector (FPD) and a thermal conductivity detector (TCD) was used to analyze gas composition, while X-ray diffraction and scanning electron microscopy were used to examine chemical phases and the dispersion pattern of the active constitutes of the sorbents. The experimental results showed that the highest desulfurization efficiency and sulfur capacity appeared at 673 K. The reactivity of the nanosized active components in the char increased with increasing the desulfurization temperature in the temperature range of 473-673 K. In the case of Fe-Mo-impregnated sorbents, Fe and Mo combined together to form complex Fe-Mo oxide phases. The introduction of Mo in the sorbent is found to greatly increase the sulfur capacity and desulfurization efficiency of the Fe sorbent supported on activated chars. The addition of Ce leads to noticeable improvement of the performance of Fe sorbent during sulfidation. The mechanisms and factors influencing the sulfidation reactions have also been discussed. © 2014 American Chemical Society.

A novel technique is described which provides quantitative and continuous analysis of light gas and condensable tar components as they are evolved in terms of carbon, hydrogen and oxygen. The technique has also been used to directly characterise the total tar sample in terms of carbon distribution and boiling point. It has been found that changes to the dynamic tar-H/C ratio correspond well with particular temperatures measured by Geiseler Plastometer for softening, maximum fluidity and re-solidification. This technique can enhance the chemical understanding of mechanisms occurring during de-polymerisation and cross-linking of coal (i.e. metaplast development and the transfer of hydrogen) while also monitoring tar evolution. A tar collection and re-vaporisation method provides a means of identifying tar groups that contribute towards the metaplast phase and temperatures at which they evolve. Both methods are unique in studying chemical aspects of coal and tar behaviour with heating, in a field based on thermo-physical techniques (e.g. H1 NMR, high temperature rheology, Geiseler plastometry, dilatation). Overall, the Dynamic Elemental Thermal Analysis (DETA) technique can give new insight into the fundamental mechanisms prevalent in coal pyrolysis and provides quantitative chemical assessment of tar nature (i) during the heating of coal and (ii) as a final (total) condensed product. © 2012 Elsevier Ltd. All rights reserved.

A fundamental study on the behaviour of heating coal macerals has been undertaken using two novel thermal analysis techniques. The apparent specific heat was determined during heating using an inverse calorimetric method (computer aided thermal analysis, CATA) and combined with pressure and displacement measurements to correlate endothermic and exothermic behaviour with measurement of swelling. The second technique used a post-oxidation stage to combust the tars and gases into products which were analysed. This method was used to study the elemental character of volatiles release from coal maceral concentrates in terms of carbon and hydrogen. Extents of swelling and exothermicity during primary devolatilisation were found to be correlated with vitrinite content and were associated with tar evolution. For the highest vitrinite fraction (of 86.4% vitrinite) swelling was initiated at the same temperature range for exothermic reactions, and maximum swelling coincided with the peak release of light gases. Tar evolution was found to change in chemical character (as defined by H/C ratio) during progressive heating, initially rising in the early stages of tar formation (<430°C) to a maximum of 1.24, then gradually decreasing to a minimum of 0.64 at 550°C. © 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Char structures evolved during the devolatilization process have been found to play a significant role in the subsequent processes (e.g., char combustion and gasification) and to influence the ash formation mechanisms. In the present paper, a mathematical model has been developed based on the multibubble mechanism to simulate the char structure evolution process. The model is the first to provide predictions of heterogenous char structures evolved during devolatilization (e.g. cenospheric char, foam structure, or dense char structure) as well as transient particle swelling ratios, based on the ultimate and proximate data of the given coal. The devolatilization process is divided into the preplastic stage, plastic stage, and resolidified stage. Bubble number conservation, mass, and force balance are formulated during the plastic stage to predict the transient swelling ratio and resultant char structures. Experiments have been conducted using a single coal particle reactor (SPR) and a drop tube furnace (DTF) with density-separated coal samples prepared using the sink-float method. The SPR experiments confirm that bubble behavior is responsible for the swelling of the particles that develop plasticity on heating. The analysis of the DTF chars shows that the swelling ratio and porosity decrease with increasing the coal density. Chars from lowdensity samples are mainly Group I chars (porosity >80%), while high-density samples yield mainly Group III chars (porosity <50%), and the medium-density samples contain a mixture. The predicted swelling ratio, porosity, and char type distribution of the chars of the density-separated samples are consistent with the experimental data.

Chars were made from four Australian coals of varying vitrinite content at pressures of 5, 10, and 15 atm. The morphology of the chars was correlated with the petrography of the parent coal. The intrinsic reaction rates of the chars at high pressures were measured, and no systematic effect of pyrolysis pressure or maceral concentration was found. It is concluded that observed variations in conversion rates under process conditions are likely to be due to char structural properties and not a result of variation in the intrinsic reactivity of the carbon in the chars. Consequently, this paper presents a char structural submodel that is integrated into an existing char combustion model to account for the combustion behavior of char particles of different morphologies. The char morphology used in the model was predicted using the developed correlation with parent coal petrography, so that a petrographic analysis as well as the proximate and ultimate analyses is required for model input. Validation of the model shows that chars produced at high pressure with a high percentage of cenospherical types burn more rapidly under process conditions than those at low pressure, with model predictions matching measurements. It is suggested that incorporating the char structural submodel into the existing char combustion model improves its predictability.

Chars were made from four Australian coals of varying vitrinite content at pressures of 5, 10, and 15 atm. The morphology of the chars was correlated with the petrography of the parent coal. The intrinsic reaction rates of the chars at high pressures were measured, and no systematic effect of pyrolysis pressure or maceral concentration was found. It is concluded that observed variations in conversion rates under process conditions are likely to be due to char structural properties and not a result of variation in the intrinsic reactivity of the carbon in the chars. Consequently, this paper presents a char structural submodel that is integrated into an existing char combustion model to account for the combustion behavior of char particles of different morphologies. The char morphology used in the model was predicted using the developed correlation with parent coal petrography, so that a petrographic analysis as well as the proximate and ultimate analyses is required for model input. Validation of the model shows that chars produced at high pressure with a high percentage of cenospherical types burn more rapidly under process conditions than those at low pressure, with model predictions matching measurements. It is suggested that incorporating the char structural submodel into the existing char combustion model improves its predictability.