Dr Arash Tahmasebi

In this second in a series of two papers, the results of tribological testing of surfaces of coke samples retrieved from an operating blast furnace were compared with those of the corresponding feed coke, to assess the impact of the conditions in the blast furnace on the abrasion resistance of coke. Tribological tests were carried out at temperatures of up to 950 °C under a controlled inert (argon) or reactive (CO2) atmosphere. Coke wear characteristics were quantified via (i) analysis of the coefficient of friction (COF) during tribological testing, and (ii) the application of microscopy and imaging techniques to the abraded specimens. The blast furnace coke sample was from the underside of the cohesive zone and is referred to as bosh coke in this paper. A near-matched feed coke was also examined. Under ambient testing conditions, the bosh coke had a lower abrasion resistance than the unreacted feed coke samples, indicating that the conditions coke is subjected to during its descent in the blast furnace effectively reduces its resistance to abrasion. Increasing the measurement temperature to 950 °C lowered the abrasion resistance of both the reactive maceral derived components (RMDC) and the inertinite maceral derived components (IMDC) in both samples. The bosh coke RMDC showed more severe damage than the IMDC, using a subjective damage severity scale. The difference in damage severity between these two phases in the bosh coke was reduced as the severity of the tribological testing conditions increased from ambient to elevated temperature (950 °C) to a reactive CO2 environment. Feed coke samples that had been pre-reacted with CO2 displayed a mean COF over time trend that was similar to that obtained from the bosh coke samples. During in-situ testing in a CO2 environment, tribo-chemical wear of the IMDC was detected, due to the surface of the IMDC reacting with the CO2 in the atmosphere. The observed tribo-chemical wear was due to the indenter and the coke surface rubbing against each other in this CO2 environment, resulting in the continuous formation and removal of reaction products. Similar trends in COF over time were observed for the bosh and feed cokes during in-situ reaction with CO2. The substantial decrease in abrasion resistance in coke at high temperature suggests that abrasion may be a more significant degradation pathway for coke in the blast furnace than hitherto expected.

This study aims to assess the impact of using green fuel in place of biodiesel on the performance and exhaust emissions of air-breathing engines. GasTurb 13 is utilized to forecast the engine's performance (kingTech 180 k turbojet engine). Catalytic deoxygenation of vegetable oils produces green diesel, offering an alternative to biodiesel. Physiochemical properties of GD blends (PME30GD20, PME20GD30, PME10GD10) were analyzed, and GasTurb-13 software predicted engine performance and emissions, validated with experimental data. The results show that GD10PME10 exhibited higher density (767.6 g/m3) than pure green fuel, while viscosity dropped by 53.85 % compared to PME. GD outperformed Jet-A1 by 0.74 % in heating value, with GD10PME10 having the highest at 42.63 MJ/kg. Engine performance measures included thrust, mass fuel flow, thrust-specific fuel consumption, and exhaust gas temperature. GD10PME10 showed a 12.5 % thrust increase and the lowest TSFC (95 g/kN.s) at 80,000 RPM compared to Jet-A1. GD20PME30 achieved the lowest EGT (550 °C) at the same RPM. Regarding emissions, GD20PME30 emitted the lowest CO (100,000 RPM, 150 ppm) and 0.5 % less CO2 (90,000 RPM) than Jet-A1. GD10PME10 produced the lowest NOx (12.5 ppm) at maximum speed, while Jet-A1 emitted the least NOx (7.5 ppm) at 120 k RPM. Overall, the data suggested that green fuel might increase the physiochemical properties of biodiesel blends, hence improving the fuel's capacity to burn more effectively in aero-engines.

Plastic waste poses a critical environmental challenge for the world. The proliferation of waste plastic coffee pods exacerbates this issue. Traditional disposal methods such as incineration and landfills are environmentally unfriendly, necessitating the exploration of alternative management strategies. One promising avenue is the pyrolysis in-line reforming process, which converts plastic waste into hydrogen. However, traditional pyrolysis methods are costly due to inefficiencies and heat losses. To address this, for the first time, our study investigates the use of microwave to enhance the pyrolysis process. We explored microwave pyrolysis for polypropylene (PP), high-density polypropylene (HDPE), and waste coffee pods, with the latter primarily comprising polypropylene. Additionally, catalytic ex-situ pyrolysis of coffee pod pyrolysis over a nickel-based catalyst was investigated to convert the evolved gas into hydrogen. The single-stage microwave pyrolysis results revealed the highest gas yield at 500 °C for HDPE, and 41 % and 58 % (by mass) for waste coffee pods and polypropylene at 700 °C, respectively. Polypropylene exhibited the highest gaseous yield, suggesting its readiness for pyrolytic degradation. Waste coffee pods uniquely produced carbon dioxide and carbon monoxide gases because of the oxygen present in their structure. Catalytic reforming of evolved gas from waste coffee pods using a 5 % nickel loaded activated carbon catalyst, yielded 76 % (by volume) hydrogen at 900 °C. These observed results were supported by elemental balance analysis. These findings highlight that two-stage microwave and catalysis assisted pyrolysis could be a promising method for the efficient management of waste coffee pods, particularly for producing clean energy.

The plastic layer permeability of five Australian coals was analyzed using two permeability measurement apparatuses operating under isothermal and thermal gradient induced coking conditions. In addition, the microstructure transitions across the plastic layers of the coals were analyzed using Synchrotron micro-CT. The permeability results and pore structure parameters derived from those analyses were correlated to better understand the mechanisms of plastic layer permeability. The high-rank coking coal with low fluidity showed a low plastic layer permeability over a wide temperature range and the generation of high internal gas pressure (IGP). Among all samples tested, the high-rank coal formed an intermediate plastic layer with the lowest number of isolated pores and the smallest size of open pores. This suggests that the lower deformability of the pore structures brought about by the low fluidity prevented additional pore growth and thus hindered pore interconnectivity. Additionally, it is possible that the low permeability in the resolidfied layer lends to pore expansion due to the difficulty of volatile release, evidenced by the larger volume of open pores within a larger size range of 50¿100 µm. It appears that the intermediate plastic layer with less interconnectivity solidified into the expanded open pore structures in the resolidified layer through the driver of high IGP, thus contributing to the low permeability. In addition, the formation of the low permeable barrier seemed to redirect the volatiles evolved from the plastic layer toward the loose coal side, which dramatically reduced the temperature range of the plastic layer during its progression from the wall to the center. These results suggest that the plastic layer permeability is influenced by several factors which affect mass transfer in the plastic layer. As such, various approaches were used in this study to observe phenomena of plastic layer permeability.

Advancements in supercritical (SC), ultrasupercritical (USC), and advanced USC coal-fired power plants have been achieved through the development of enhanced materials utilized in advanced steam cycles and through the deployment of advanced emission control systems. These are referred to as high-efficiency low-emission (HELE) technologies, which may solve numerous issues associated with coal-based power generation. There is a clear global transition from subcritical to advanced power plant types and significant R&D work on HELE technologies. Therefore, this comprehensive review covers the latest HELE technology deployment in major coal-consuming countries and their R&D roadmaps to advance HELE technologies. In spite of the various advantages of HELE technologies, there have been numerous technical challenges relevant to achieving the HELE steam conditions and deploying low emission control technologies in the HELE systems. Hence, this review covers the technical challenges and the relevant recent research by using various coal combustion test facilities. The current focus for the progression from USC boilers to advanced USC boilers is a successful demonstration of the developed high-performance alloys under the advanced steam conditions. This review covers the current status of research and development of advanced USC (A-USC) materials and challenges based on the major material research programs.

Hydrogen rich gas production and advantages of polygeneration during biomass conversation through pyrolysis were extensively reviewed in this paper. Different innovative pyrolysis setups and the effect of reaction conditions such as pressure, temperature, catalyst type, biomass type, and reactor type on the formation of hydrogen and other value-added chemicals has been exploited. High temperatures and pressures together with application of catalysts was reported to favour the enhancement of hydrogen by promoting secondary pyrolysis reactions and hence the production of H2 gas. Compared to one-stage pyrolysis systems, pyrolysis data from two-stage pyrolysis reaction systems reported improved production of hydrogen and value-added chemicals due to the reforming of volatile matter in the second stage reactor. The polygeneration effect of biomass pyrolysis has also been reviewed, and it was observed that the polygeneration systems were significantly vital in covering the demand and supply of renewable energy.

The blast furnace technology is still the main ironmaking route with a current global share of 70%. Reduction of fossil carbon consumption and CO2 emissions in blast furnace operations are essential for the decarbonization of steelmaking. Potential solutions such as introducing renewable carbon-based materials (torrefied biomass, charcoal), using hydrogen-enriched reducing gases (i.e., hydrogen gas, coke oven gas, reformed coke oven gas, green methane), oxygen enrichment with top gas recycling, and carbon capture and storage/utilization have been considered to decrease emissions. The enhanced sustainability of blast furnace operations depends primarily on improving the hydrogen-to-carbon replacement ratio. Hydrogen is an effective reducing agent, producing steam during the reduction of ferrous burden. The replacement of coke and PCI with hydrogen leads to reduced fuel rates and CO2 emissions. Although implementing the innovative ironmaking solutions reduces coke and coal consumption, coke cannot be replaced entirely as it plays an irreplaceable role as a mechanical support network and the permeable layer for gas movement in the blast furnace. The injection of alternative reducing agents into the blast furnace alters the reaction environment by changing gas composition and temperature. Therefore, understanding the impacts of new reaction conditions on coke rate and quality requirements is important to both coal producers and steel manufacturers. This paper reviews the current understanding of how the introduction of alternative reducing agents into the blast furnace influences the gasification behavior, degradation mechanism, and consumption rate of coke. The review also identifies the knowledge gaps and future research opportunities in the field.

N-doped highly porous carbons (NHPCs) derived from Victorian brown coal (VBC) were prepared through direct KOH activation in the presence of urea as the N source. Different weight ratios of KOH (VBC-urea mixture: KOH=1:0, 1:1, 1:2, and 1:3) have been used to optimize the porosity of NHPCs. Benefiting from the synergistic effect of the high porosity and N doping, the synthesized material with a high specific surface area of 687 m2/g and the N content at ~11 at% exhibited a high specific discharge capacity of 604.6 mAh/g at a current density of 0.1 A/g after 100 cycles and a high-rate performance of 245 mAh/g at 3 A/g. The developed material delivered a reversible capacity of 707.7 mAh/g at 0.05 A/g at the end of rate performance. The long-term cycling test performed at 1 A/g illustrates a stable and reversible capacity of 268 mAh/g after 1000 cycles with a coulombic efficiency of 100% and charge retention of 88%. The hierarchically porous carbon matrix with N doping can increase the Li+ diffusion efficiency and accelerate the charge transfer, thus leading to enhanced high-rate performance, superior reversibility, and high cyclic stability.

High-efficiency, low-emissions (HELE) coal-fired power plant technologies operate with a higher thermal efficiency of the steam cycle for coal-fired power generation, reducing CO2 emissions per unit energy generation. They represent some of the primary and intermediate solutions to the world's energy security. Extensive numerical modeling efforts have been undertaken over the past several decades, which have increased our understanding of the technical problems in HELE boilers, including combustion and boiler performance optimization, ash deposition, and material problems at higher operating temperatures and pressures. Overall, the differences in the physical and chemical models, boiler performance, and ash deposition of oxy-fuel combustion in HELE boilers that recirculate CO2 and H2O in the boilers are also discussed in comparison with the combustion of coal in the air. This Review comprehensively summarizes the current research on numerical modeling to offer a better understanding of the technical aspects and provides future research requirements of HELE coal-fired boilers, including boiler performance optimization, ash deposition, and material problems. The effects of changes in the configuration and operating conditions are discussed, focusing on the optimization of boiler performance in aspects such as unburnt carbon and NOx emissions. The paper also reviews the retrofit and optimization of operating conditions and the burner geometry with the low-NOx coal combustion technologies necessary to operate the HELE power plants. In terms of ash deposition, the development of submodels, including particle sticking and impacting behaviors and their effects on the deposit growth predictions under different temperatures, are discussed. Numerical models of the material oxidation and creep in the austenitic and nickel-based alloys generally used in HELE conditions have been developed using the finite element method to predict the availability of advanced alloys and creep life in the actual service time of the boiler parts. The predictions of oxide scale growth and exfoliation on the steam-side and fire-side and the creep strength are analyzed. The review also identifies some further research requirements in numerical modeling to achieve the optimization of coal combustion processes and address the technical problems in advanced HELE power plant operations.

A few-layer graphene (FLG) composite material was synthesized using a rich reservoir and low-cost coal under the microwave-assisted catalytic graphitization process. X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy were used to evaluate the properties of the FLG sample. A well-developed microstructure and higher graphitization degree were achieved under microwave heating at 1300¿ C using the S5% dual (Fe-Ni) catalyst for 20 min. In addition, the synthesized FLG sample encompassed the Raman spectrum 2D band at 2700 cm-1, which showed the existence of a few-layer graphene structure. The high-resolution TEM (transmission electron microscopy) image investigation of the S5% Fe-Ni sample confirmed that the fabricated FLG material consisted of two to seven graphitic layers, promoting the fast lithium-ion diffusion into the inner surface. The S5% Fe-Ni composite material delivered a high reversible capacity of 287.91 mAhg-1 at 0.1 C with a higher Coulombic efficiency of 99.9%. In contrast, the single catalyst of S10% Fe contained a reversible capacity of 260.13 mAhg-1 at 0.1 C with 97.96% Coulombic efficiency. Furthermore, the dual catalyst-loaded FLG sample demonstrated a high capacity¿up to 95% of the initial reversible capacity retention¿after 100 cycles. This study revealed the potential feasibility of producing FLG materials from bituminous coal used in a broad range as anode materials for lithium-ion batteries (LIBs).

The changes in chemical structures over the plastic layer region during the coking of coals have a significant impact on coke formation and coke quality. This paper employed the Solid-state 13Carbon Nuclear Magnetic Resonance (13C NMR), and the Synchrotron attenuated total reflection Fourier transform infrared (ATR-FTIR) microspectroscopy (Synchrotron IR) to study the transformation of the chemical structures in plastic layer samples. The light gases (mainly methane and hydrogen) released from coking process were analyzed using micro gas chromatography (micro-GC) connected to a small coking reactor heated in an electric furnace that simulated the formation of the plastic layers. The results show clearly that the total aromaticity increased consistently in the plastic layers for all coals tested, while the amounts of side-chains decreased significantly during the plastic layer. There was a clear trend showing that the total number of bridge bonds and the looped structures, indicating that the degree of cross-linking would increase through the plastic layer. The plastic layer samples from low fluidity exhibited cross-linking structures with a high degree of branching and aromaticity, while those from high fluidity coals formed cross-linking structures with a relatively low degree of aromaticity and branching but with a large number of bridge bonds and looped structures. The transferable methyl, methylene and hydrogen were strongly correlated to the cross-linking reaction and side-chain elimination in the thermoplastic region, which is reflected by the release profiles of methane and hydrogen gas during the plastic layer stage.

The present dataset describes the entrained-flow pyrolysis of Microalgae Chlorella vulgaris and the results obtained during bio-char characterization. The dataset includes a brief explanation of the experimental procedure, experimental conditions and the influence of pyrolysis conditions on bio-chars morphology and carbon structure. The data show an increase in sphericity and surface smoothness of bio-chars at higher pressures and temperatures. Data confirmed that the swelling ratio of bio-chars increased with pressure up to 2.0 MPa. Consequently, changes in carbon structure of bio-chars were investigated using Raman spectroscopy. The data showed the increase in carbon order of chars at elevated pressures. Changes in the chemical structure of bio-char as a function of pyrolysis conditions were investigated using FTIR analysis.

The transformation of nitrogen in microalgae during entrained-flow pyrolysis of Chlorella vulgaris was systematically investigated at the temperatures of 600¿900 °C and pressures of 0.1¿4.0 MPa. It was found that pressure had a profound impact on the transformation of nitrogen during pyrolysis. The nitrogen retention in bio-char and its content in bio-oil reached a maximum value at 1.0 MPa. The highest conversion of nitrogen (50.25 wt%) into bio-oil was achieved at 1.0 MPa and 800 °C, which was about 7 wt% higher than that at atmospheric pressure. Higher pressures promoted the formation of pyrrolic-N (N-5) and quaternary-N (N-Q) compounds in bio-oil at the expense of nitrile-N and pyridinic-N (N-6) compounds. The X-Ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) results on bio-chars clearly evidenced the transformation of N-5 structures into N-6 and N-Q structures at elevated pressures. The nitrogen transformation pathways during pyrolysis of microalgae were proposed and discussed.

Oxy-fuel combustion of solid fuels is seen as one of the key technologies for carbon capture to reduce greenhouse gas emissions. The combustion characteristics of lignite coal, Chlorella vulgaris microalgae, and their blends under O2/N2 and O2/CO2 conditions were studied using a Thermogravimetric Analyzer-Mass Spectroscopy (TG-MS). During co-combustion of blends, three distinct peaks were observed and were attributed to C. vulgaris volatiles combustion, combustion of lignite, and combustion of microalgae char. Activation energy during combustion was calculated using iso-conventional method. Increasing the microalgae content in the blend resulted in an increase in activation energy for the blends combustion. The emissions of S- and N-species during blend fuel combustion were also investigated. The addition of microalgae to lignite during air combustion resulted in lower CO2, CO, and NO2 yields but enhanced NO, COS, and SO2 formation. During oxy-fuel co-combustion, the addition of microalgae to lignite enhanced the formation of gaseous species.

Catalytic microwave pyrolysis of peanut shell (PT) and pine sawdust (PS) using activated carbon (AC) and lignite char (LC) for production of phenolic-rich bio-oil and nanotubes was investigated in this study. The effects of process parameters such as pyrolysis temperature and biomass/catalyst ratio on the yields and composition of pyrolysis products were investigated. Fast heating rates were achieved under microwave irradiation conditions. Gas chromatography-mass spectrometry (GC-MS) analysis of bio-oil showed that activated carbon significantly enhanced the selectivity of phenolic c3/30/2016 4:14:58 PMompounds in bio-oil. The highest phenolics content in the bio-oil (61.19 %(area)) was achieved at 300 °C. The selectivity of phenolics in bio-oil was higher for PT sample compared to that of PS. The formation of nanotubes in PT biomass particles was observed for the first time in biomass microwave pyrolysis.

The production of bio-oil rich in methoxyaromatics during catalytic pyrolysis of Eucalyptus pulverulenta (EP) was studied using a fixed-bed reactor in the temperature range of 300¿500 °C and the bio-oil composition was analyzed by using a GC¿MS. The results showed that the highest bio-oil yield of 38.45 wt% was obtained at 400 °C in the presence of Na2CO3, and the concentration of methoxyaromatics reached the maximum value of 63.4%(area) in the bio-oil. The major methoxyaromatics identified in bio-oil were guaiacol, syringol, 4-ethyl-2-methoxy phenol, and 1,2,4-trimethoxybenzene. The analysis of gaseous products indicated that CO2 was the major gas at low-temperatures and concentrations of H2 and CH4 increased with increasing pyrolysis temperature. Na2CO3 promoted the formation of methoxyaromatics, while NaOH seems to have enhanced the formation of phenolics. The mechanism of the formation of methoxyaromatics during pyrolysis of EP was proposed.

In this paper, the use of lignite char as the reductant is proved to be promising in direct reduction of iron (DRI) technology. A better understanding of the reducing characteristics of lignite char is necessary for the development of efficient DRI technologies. The application of lignite char as reductant in direct reduction of hematite has been investigated in this study, and the results are compared with those of lignite coal and graphite. Thermogravimetric analysis was used to analyze the thermal behavior of the composite pellets. Maximum iron oxide reduction rate occurred at 865, 829.5, and 920 °C when lignite coal, lignite char, and graphite were used as reductants, respectively, indicating that iron oxide can be reduced at lower temperatures in the presence of lignite char. X-ray diffraction analysis showed that complete reduction of hematite to elemental iron was achieved with lignite char after 15-min reduction at 1000 °C. Scanning electron microscopy-energy-dispersive X-ray analysis results showed that the atomic ratio of Fe/O was increased from 0.39 in pellets before reduction to 0.51, 0.55, and 0.71 after reduction by graphite, coal, and lignite char, indicating that lignite char reduced hematite to a higher degree compared to lignite coal and graphite.

Pore structure changes during pre-drying of lignite affect its low-temperature oxidation and increase the susceptibility to spontaneous combustion. In this study, the effects of drying methods (i.e., vacuum drying and N2 drying) on self-heating of Indonesian lignite during oxidation were investigated using a dual fixed-bed quartz reactor. The variation of coal temperatures was recorded and the release of CO2 and CO was measured by a gas chromatography. The pore volume and surface area of dried samples were measured using Brunauer-Emmett-Teller (BET) method. Mesopores in lignite initially increased and collapsed with further increasing drying intensity during drying in N2, resulting in a rapid self-heating rate of lignite within a critical moisture content range of 6-13%. However, vacuum drying caused a gradual increase in mesopores, which lead to a monotonic increase in self-heating rate with decreasing residue moisture content in lignite. The experimental results indicated that the production rates of both CO2 and CO during oxidation of raw lignite increased with reducing particle size and increasing gas flow rate, but decreased at lower moisture contents. Typically, the variation of production rates of both CO2 and CO as a function of particle size and gas flow rate followed a similar trend to that of raw lignite when the lignite was completely dried by the vacuum drying method. The impacts of lignite particle size and gas flow rate on the yields of CO2 and CO was limited due to less diffusion of O2 into small pores, suggesting that the oxidation reaction between lignite and oxygen has been shifted from diffusion controlled to kinetic controlled reactions.

The development of lignite-char-supported metal oxide catalyst for reduction of nitric oxide (NO) is investigated in this paper. The characteristics of NO reduction by copper and iron oxide catalysts supported on activated lignite chars (ALC) was studied using a fixed-bed reactor at 300 °C. The results showed that the impregnation of Cu on ALC resulted in higher catalytic reactivity during NO reduction compared with that of Fe. Chemisorption of O2 and NO on Cu/ALC catalyst was found to play an important role in denitrification. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses showed that chemically adsorbed oxygen facilitates the formation of C(O) complex and oxidation of Cu0 to Cu+ for Cu/ALC catalyst. The C(O) intermediates and C*production formed due to the fact that C/O2 reaction promoted the reduction of NO. It is suggested that the catalytic reaction of NO in this case comprised of C/O2 reaction, C(O)/NO reaction and formation of N2 and CO2. Cu seemed to have significantly promoted the C(O) formation and CO oxidation compared with Fe. The catalytic reactivity of Cu species for C(O) formation and CO oxidation followed the order of Cu0 > Cu+ > Cu2 +. Fe3O4 was believed to be the active phase in Fe catalyst. The oxygen and char-supported metal catalysts significantly promoted C/NO reaction, and therefore may lead to a lower operation temperature of NOx removal.

Catalytic fixed-bed and microwave pyrolysis of palm kernel shell using activated carbon (AC) and lignite char (LC) as catalysts and microwave receptors are investigated. The effects of process parameters including temperature and biomass:catalyst ratio on the yield and composition of pyrolysis products were studied. The addition of catalyst increased the bio-oil yield, but decreased the selectivity of phenol in fixed-bed. Catalytic microwave pyrolysis of PKS significantly enhanced the selectivity of phenol production. The highest concentration of phenol in bio-oil of 64.58 %(area) and total phenolics concentration of 71.24 %(area) were obtained at 500 °C using AC. Fourier transform infrared spectroscopy (FTIR) results indicated that concentration of OH, C. H, C. O and C. O functional groups in char samples decreased after pyrolysis. Scanning electron microscopy (SEM) analysis clearly indicated the development of liquid phase in biomass particles during microwave pyrolysis, and the mechanism is also discussed.

The sulfidation and regeneration properties of lignite char-supported iron-based sorbent for coke oven gas (COG) desulfurization prepared by mechanical stirring (MS), ultrasonic assisted impregnation (UAI), and high pressure impregnation (HPI) were investigated in a fixed-bed reactor. During desulfurization, the effects of process parameters on sulfidation properties were studied systematically. The physical and chemical properties of the sorbents were analyzed by X-ray diffraction (XRD), scanning electron microscope coupled with energy dispersive spectroscopy (SEM-EDS), Fourier transform infrared (FTIR) and BET surface area analysis. The results of desulfurization experiments showed that high pressure impregnation (HPI) enhanced the sulfidation properties of the sorbents at the breakthrough time for char-supported iron sorbents. HPI method also increased the surface area and pore volume of sorbents. Sulfur capacity of sorbents was enhanced with increasing sulfidation temperatures and reached its maximum value at 400 °C. It was observed that the presence of steam in coke oven gas can inhibit the desulfurization performance of sorbent. SO2 regeneration of sorbent resulted in formation of elemental sulfur. HPIF10 sorbent showed good stability during sulfide-regeneration cycles without changing its performance significantly.

The effect of moisture content on ignition and combustion behavior of Chinese (HL) and Indonesian (YN) lignite were investigated. Particles with a size range of 75¿105 µm with different moisture contents were injected in a bench-scale, electrically heated transparent reactor and the combustion of individual particles was observed with a high-resolution high-speed camera. Direct ignition observations indicated that most of the HL lignite particles underwent extensive fragmentation during ignition. Fragmentation was attributed to the explosive diffusion of volatiles and water vapor to the particle surface as a result of fast heating rate. Fragmentation reduced the particle size and increased the possibility of heterogeneous ignition of individual fragments. YN lignite particles on the other hand, underwent one-mode whole particle ignition upon heating. Higher moisture content caused a significant ignition delay in both lignite samples. 10% and 20% moisture in lignite samples resulted in around 83 and 160 ms delay in ignition for both coals. Higher intensity of fragmentation of HL particles during combustion compared to YN lignite resulted in shorter total particle combustion time at higher moisture contents. The findings of this study advanced the knowledge of the effects of moisture on ignition and combustion of low-rank coals.

The effects of physical structure (pore structure) on behavior of water in lignite coal and activated carbon (AC) samples were investigated by using Differential Scanning Calorimetry (DSC) and low-temperature X-ray diffraction (XRD) techniques. AC samples with different pore structures were prepared at 800 °C in steam and the results were compared with that of parent lignite coal. The DSC results confirmed the presence of two types of freezable water that freeze at -8 °C (free water) and -42 °C (freezable bound water). A shift in peak position of free water (FW) towards lower temperature was observed in AC samples compared to the lignite coal with decreasing water loading. The amount of free water (FW) increased with increasing gasification conversion. The amounts of free and freezable bound water (FBW) in AC samples were calculated and correlated to pore volume and average pore size. The amount of FW in AC samples is well correlated to the pore volume and average pore size of the samples, while an opposite trend was observed for FBW. The low-temperature XRD analysis confirmed the existence of non-freezable water (NFW) in coal and AC with the boundary between the freezable and non-freezable water (NFW) determined.

An Indonesian lignite was oxidized using a dual fixed-bed quartz reactor to examine the effect of moisture content, particle size and gas flow rate on low-temperature oxidation characteristics. The self-heating characteristics of dried samples have been further systematically investigated. During oxidation experiments, the temperature profiles of coal were recorded and CO2 and CO gases were analyzed using gas chromatography. The temperature of coal samples in air increased monotonically, successively exceeding the separation point temperature (SPT) and the crossing point temperature (CPT). SPT, the initial point of self-heating during oxidation, significantly depends upon water content of coal and its removal during drying. It was found from the SPT values that oxidation rate of lignite was highest at moisture content between 6% and 13%. The CO2 and CO production rates during the self-heating process increased with decreasing particle size, but these effects decreased gradually with increasing drying intensity due to "pore collapse" of lignite during drying. Both SPT and CPT for each dried samples decreased with decreasing particle size, indicating a more rapid self-heating at smaller particle size. The progressive decrease in dependence of the CO2 and CO production rates on gas flow rate with increasing drying intensity indicated that drying causes the transition of oxidation reactivity controlled by bulk diffusion to that by oxidation kinetics, which altered the net effect of heat loss and supply of oxygen in response to increasing gas flow rate, even resulting in change of the critical moisture range at high gas flow.

In this paper, the regeneration characteristics of activated-char-supported Fe-Zn-Cu sorbents were studied. The desulfurization and regeneration experiments were carried out using a quartz fixed-bed reactor at ambient pressure. The effects of regeneration conditions, such as space velocity, temperature, and steam concentration, on the regeneration performance were examined. The crystal phase, chemical structure of activated components, and physical structure of sorbents before and after regeneration were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) surface area. The experimental results indicated that the char-supported Fe-Zn-Cu sorbents can be regenerated at temperatures above 500 °C. The optimal regeneration parameters with a space velocity of 5000 h-1, temperature of 700 °C, and steam concentration of 50 vol % have been obtained. The result of regeneration by steam suggested that the BET surface area of the sorbent after regeneration was larger than that of the fresh sorbent, and steam can restore the physical structure of the sorbent and expand its aperture during regeneration. Regeneration using SO2 was also studied under the optimal conditions. The XRD, FTIR spectroscopy, and XPS analyses indicated that the composite metal oxides in the sorbent formed during sulfidation were transformed into metal sulfides, which can be converted back to metal oxides during regeneration.

¿-Sialon based composites were produced using a vertical reactor by carbothermal reduction reaction under nitrogen using fly ash and lignite chars to examine the effects of mixing, carbon content, reaction temperature and sintering time. The influences of chars as a reductant were further investigated in comparison with graphite. The evolution of phase and morphology in samples were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). Mechanical stirring was favored to mix fly ash and chars, while ball-milling shove the chars with porous structure due to collisions of agate balls, preventing N2 penetration to the inner parts of reactants. When excess carbon was increased to 100%, a higher combustion reactivity of low-temperature chars resulted in the production of SiC phase. The evolution of ¿-Sialon with increasing reaction temperature showed the samples mixed with chars were more sensitive to reaction temperature than that with graphite. ¿-Sialon phase increased gradually with increasing sintering time to 6 h and decreased thereafter due to the decomposition or conversion of ¿-Sialon. These changes were more significantly for samples adding lignite chars. The optimal operation has been determined and rod-like ¿-Sialon whiskers with high aspect ratio appeared after performing the operation. In the growth process of whiskers, bead-shape whiskers were observed, suggesting that the growth mechanism was different from the conventional vaporliquidsolid (VLS) mechanism.

The desulfurization properties of Fe-Zn sorbent prepared by impregnating Fe and Zn into lignite char via ultrasonic-assisted impregnation (UAI) were investigated in comparison with the mechanical stirring (MS) method. The sulfidation experiments were carried out using a fixed-bed quartz reactor under ambient pressure. The amounts of metals loaded into char were measured by inductively coupled plasma atomic emission spectrometry (ICP-AES). The crystalline phases and chemical structure of sorbents before and after sulfidation were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), respectively. The morphology of sorbents was analyzed by using scanning electron microscope (SEM) with an energy dispersive X-ray (EDX) auxiliary. The experimental results showed that metal oxides as the active components were evenly dispersed on char as nanoparticles. The impregnation of active components was significantly improved by the ultrasonic-assisted impregnation method. When sorbents were prepared by ultrasonic-assisted impregnation, the metal oxide particles became smaller and more evenly dispersed on the char matrix which resulted in higher desulfurization efficiency and sulfur uptake capacity of the sorbents. The BET results showed that the physical properties of sorbents (surface area and pore volume) significantly improved when prepared by UAI method compared to MS method. The sulfidation temperature had a significant effect on desulfurization performance of char supported sorbents. The Fe:Zn molar ratio of 2:1, and impregnation time of 9 h were suggested as the optimal preparation conditions during ultrasonic-assisted impregnation.

Pyrolysis characteristics of four algal and lignocellulosic biomass samples were studied by using a thermogravimetric analyzer (TGA) and a fixed-bed reactor. The effects of pyrolysis temperature and biomass type on the yield and composition of pyrolysis products were investigated. The average activation energy for pyrolysis of biomass samples by FWO and KAS methods in this study were in the range of 211.09-291.19kJ/mol. CO2 was the main gas component in the early stage of pyrolysis, whereas H2 and CH4 concentrations increased with increasing pyrolysis temperature. Bio-oil from Chlorella vulgaris showed higher content of nitrogen containing compounds compared to lignocellulosic biomass. The concentration of aromatic organic compounds such as phenol and its derivatives were increased with increasing pyrolysis temperature up to 700°C. FTIR analysis results showed that with increasing pyrolysis temperature, the concentration of OH, CH, CO, OCH3, and CO functional groups in char decreased sharply.

Sulfidation properties of char-supported Fe-Zn-Mo sorbents prepared by ultrasonic impregnation method were investigated during simultaneous removal of H<inf>2</inf>S and COS from coke oven gas (COG) using a fixed-bed quartz reactor. Sorbent samples before and after sulfidation were analyzed using X-Ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The experimental results showed that the addition of Mo significantly improved the desulfurization properties (i.e., breakthrough time, sulfur capacity and desulfurization efficiency) of Fe-Zn sorbents. Desulfurization reactions were exothermic and thermodynamically favorable in the temperature range of 200¿400 °C. Thermodynamic analysis of the sorbents indicated that higher concentration of H<inf>2</inf>S and lower concentration of H<inf>2</inf> favors the reaction of metal oxides with H<inf>2</inf>S to form metal sulfides.

Microwave (MW) pyrolysis of algal and lignocellulosic biomass samples were studied using a modified domestic oven. The pyrolysis temperature was recorded continuously by inserting a thermocouple into the samples. Temperatures as high as 1170 and 1015°C were achieved for peanut shell and Chlorella vulgaris. The activation energy for MW pyrolysis was calculated by Coats-Redfern method and the values were 221.96 and 214.27kJ/mol for peanut shell and C. vulgaris, respectively. Bio-oil yields reached to 27.7wt.% and 11.0wt.% during pyrolysis of C. vulgaris and peanut shell, respectively. The bio-oil samples from pyrolysis were analyzed by a gas chromatography-mass spectrometry (GC-MS). Bio-oil from lignocellulosic biomass pyrolysis contained more phenolic compounds while that from microalgae pyrolysis contained more nitrogen-containing species. Fourier transform infrared spectroscopy (FTIR) analysis results showed that concentration of OH, CH, CO, OCH3, and CO functional groups in char samples decreased significantly after pyrolysis.

This paper presents a hybrid algorithm based on invasive weed optimization (IWO) and particle swarm optimization (PSO), named IW-PSO. IWO is a relatively novel numerical stochastic optimization algorithm. By incorporating the reproduction and spatial dispersal of IWO into the traditional PSO, exploration and exploitation of the PSO can be enhanced and well balanced to achieve better performance. In a set of 15 test function problem, the parameters of IW-PSO were analyzed and selected, and the computational results show that IW-PSO can effectively obtain higher quality solutions so as to avoid being trapped in local optimum, comparing with PSO and IWO. © (2013) Trans Tech Publications, Switzerland.