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The analysis of the macromolecular structure and morphology in coal during oxidation is the basis to explore the mechanism of spontaneous combustion. To explore the evolutionary rules of coal macromolecular structure during oxidation, Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Raman Spectroscopy (Raman) were employed to analyze the coal samples with different oxidation degrees. The results revealed that the oxidation action led to the decrease of the aliphatic structures and aromatic hydroxyl groups in coal, while promoting the formation of oxygen-containing functional groups and aromatic structures. It also led to a relative increase of free hydroxyl groups linked to hydrogen bonds. The aromatic layer spacing (d 002) decreased with increasing oxidation degree, while the microcrystal stacking height (L c), the aromatic layer diameter (L a), the average number of crystal stacking layers (n) generally increased. It indicated that small aromatic ring molecules in coal could undergo continuous polymerization during oxidation to form a single aromatic layer structure. The variation of Raman spectrum parameters exhibited a consistent decreasing trend in W D /W G , I D /I G, A D /A G , and A (GR+SL) /A G value, indicating an increase in the vibration of sp2 hybridization carbon atoms within the lattice structure of coal. Conversely, P G-D , A S /A D and A (GR+VL+VR) /A D value increased overall, suggesting that small aromatic rings decreased in content during oxidation while polymerizing into larger aromatic rings. The coal structure underwent a brief stage of disordered evolution during oxidation, followed by removal of impurity structures and condensation of aromatic structures due to increasing oxidation temperatures, ultimately leading to a highly ordered crystalline state. The oxidation process significantly influenced the development of coal's aromatic structure, particularly in less metamorphic coal. The research findings provide a theoretical basis for analyzing the underlying mechanism behind spontaneous combustion induced by coal oxidation. • The structure of lignite coal and bituminous coal with different oxidation degrees were characterized. • Oxidation action results in the maturation of aromatic system in coal. • The evolution rule of coal macromolecular structure is dynamic during oxidation. • Coal underwent a transient disordered stage before progressing toward a highly ordered crystalline state. [ABSTRACT FROM AUTHOR]

The oxidation reaction order (n) and activation energy (E a) are the primary parameters in the global carbon/oxygen reaction model. However, these parameters continue to be a subject of argument due to the problems of experimental technology and kinetic analysis methods. This paper used a micro fluidized bed reaction analysis system to study the reaction kinetics of bituminous coal char with a median particle size of 75 μm at 923–1223 K and 2%–21% oxygen concentration. The effects of temperature and oxygen concentration on the combustion characteristics of char were analyzed. The real n value and main kinetic parameters in the n th-order Arrhenius model were measured, and the transition temperatures of the combustion control zone were determined. Results showed that the position of the maximum combustion reactivity occurs in the range of 20–30% of carbon conversion, which decreased slightly with the increase of temperature and increased slightly with the increase of oxygen concentration. The intrinsic reaction zone is below 1023 K, the intrinsic reaction order is between 0.64 and 0.71, and the intrinsic activation energy is about 106 kJ/mol. This study contributes to improve the precision and practicality of the n th-order Arrhenius model. • Measured the real reaction order n and main kinetic parameters of coal char by a micro fluidized bed system • Determined the transition temperatures of the combustion control zone, and the intrinsic reaction zone I is below 1023 K • The n value at the same conversion in the same combustion control zone is almost the same • In zone I n =0.64–0.71, activation energy E a =97–117 kJ/mol, pre-exponential factor A 0 =130–836 mol/(s·m2·atm n) [ABSTRACT FROM AUTHOR]

Iron-ore pelletizing plants use high-rank coals to supply the heat necessary to process ores. Ash material from coal, in combination with iron-ore dust originating from the disintegration of the pellets, can cause deposition/slagging which often leads to severe production losses and damage. Deposition/slagging is most prominent in the hot areas of the grate-kiln setup and is more severe at the inlet of the rotary-kiln, i.e., the transfer-chute. Following on from our previous work, high-rank bituminous coals with potential for use in the pelletizing process were combusted in a pilot-scale (0.4 MW) pulverized-coal fired experimental combustion furnace (ECF). The fly-ash particles and short-term deposits were characterized to shed light on the observed difference in slagging/deposition tendencies of the coals. Global thermodynamic equilibrium modeling, in combination with viscosity estimates, was used to interpret the experimental findings and investigate the effect of the coal-ash composition upon deposition/slagging. This approach was carried out with and without the presence of Fe 2 O 3 -rich pellet-dust under oxidizing conditions within the temperature range at the transfer-chute of iron-ore pelletizing rotary-kilns. Based on the findings, a Qualitative Slagging Indicator (QSI) was proposed that can help pre-screen new solid fuels for potential slagging issues. The proposed QSI highlights the following: (1) an inverse relationship between viscosity and slagging/deposition tendency of the coals was observed (2) as viscosity decreases (either with increasing temperature or due to the change in the coal-ash composition), stronger deposits will form that will complicate the mechanical removal of the deposited layer. It was therefore inferred that low viscosity molten phases facilitate deposition/slagging, which is exacerbated by the presence of fluxing agents (e.g., CaO, MgO, K 2 O, Na 2 O, and Fe 2 O 3) in the deposits. The low viscosity coal-ash-induced molten phases are also more likely to interact with the Fe 2 O 3 -rich pellet-dust that results in further decreases in viscosity, thereby intensifying depositions. The results from this work complement the on-going research by our group to elucidate and alleviate ash-related problems in industrial grate kilns. • The proposed QSI can pre-screen new solid-fuels for potential slagging issues. • Coal-ash composition plays a significant role in the formation of sintered deposits. • An inverse relationship between viscosity and slagging tendency was observed. • The presence of fluxing agents in the deposits facilitates slagging. • Low-viscosity molten phases in coal-ash are more likely to interact with pellet-dust. [ABSTRACT FROM AUTHOR]

Abstract This study aims to show how fractal analysis applied to nitrogen and carbon dioxide adsorption isotherms helps to understand the textural changes during char activation. The materials under study were two series of activated carbons obtained by means of CO 2 gasification of chars at 1123 K. The chars were obtained through carbonization at 1123 K of a high-volatile A bituminous coal that was previously oxidized in air at 543 and 473 K for periods of time from 0 up to 14 days. The fractal analysis of CO 2 and N 2 adsorption data corresponding to activated carbons is carried out by using the approaches of Neimark and Wang-Li. Fractal and other textural characteristics of the series of activated carbons are put side by side with those of the series of the corresponding chars. Pore network development through activation depends on the extent of the air preoxidation of the precursor coal as this step conditions the textural properties of the carbonized materials that also determine the behaviour during activation. Fractal and other textural characteristics indicate that coal preoxidation at 543 K leads to chars that are more stable during activation than those obtained from coals preoxidized at 473 K. The changes in fractal dimensions caused by gasification can be explained taking into account the classical textural properties, the effect of gasification and also the pore structure of the precursor char. The gasification process itself produces a decrease in fractal dimensions and the existence of non-accessible porosity in chars may contribute to an increase in fractal dimensions during activation. The prevalence of the smoothening effect of char gasification was found to be more important for the zones of the narrowest pores. Consequently, variation of fractal characteristics as a consequence of gasification depends on the technique employed for the analysis: CO 2 , N 2 adsorption or mercury porosimetry. Highlights • Gasification and char texture condition textural evolution during char activation. • Fractal changes during gasification depend on pore size region considered. • Smoothening effect of char gasification becomes more evident for smaller pore sizes. • Chars from coals oxidized at higher temperature have more structural stability. [ABSTRACT FROM AUTHOR]

Abstract In this study, the effects of two biomass ashes (corn stalk (CS) and wood pellet (WP)) on the sintering behaviors of two types of coal (high melting Shanxi coal (SX) and low melting Shenhua coal (SH)) were investigated in a horizontal chamber furnace. The results show that CS 10%, CS 50%, and WP 10% promote the ash sintering of SX coal ash and SH coal ash, while WP 50% inhibits the sintering of SH coal ash. The higher blend ratio of CS ash strengthens the promoting effects on sintering of both coals. According to the results of SEM-EDX and XRD, the low blend ratio of biomass ash has limited influence on chemical compositions and minerals distribution of SX ash. Anorthite and low melting albite generate after adding 50% CS, which promotes the sintering of SX ash. 50% WP promotes the conversion of mullite to anorthite and gehlenite of SX ash by significantly increasing the content of calcium. CS ash promotes SH ash sintering by accelerating the formation of diopside and amorphous minerals. XRD analysis revealed that the calcium plays a vital role during the sintering of high blend ratio of WP. Highlights • Corn stalk promoted the sintering of coal ash, the effects increased with the increasing of corn stalk ash content. • 50 % wood pellet promoted the ash sintering of Shanxi coal, inhibited the sintering of Shenhua coal. • Calcium played a key role during the sintering of high blend ratio of wood pellet. [ABSTRACT FROM AUTHOR]

Abstract The multistep solvent extraction is an effective way for evaluating the original structure of coal, however, it is seldom used for studying the Hg distribution in coal and its release behavior during mild pyrolysis process. In this work, the Guizhou bituminous coal was divided into organic-rich class C 1 and minerals-rich class C 2 , the C 1 was further subdivided into 4 groups (EG 1 –EG 4) using multistep solvent extraction method. The Hg species in different samples and their fate during pyrolysis was investigated using sequential chemical leaching methods and temperature-programmed experiments. The results showed the dominant Hg forms in different samples are quite different, the HCl-soluble and HNO 3 -soluble Hg are the dominant forms in C 2 , while organic matrix combined Hg is the most abundant form in C 1 , EG 1 and EG 2 samples. The Hg contents in EG 1 to EG 4 groups are in the order of EG 4 < EG 3 < EG 2 < EG 1 , and have little correlation with the total sulfur contents. The thermal stability of different Hg species are quite distinct, the Hg in EG 1 sample is the most thermal unstable and almost released completely before 400 °C. The Hg release of GZB, C 1 , and C 2 are similar, >60% and 95% of Hg in the three samples can be released at 400 °C and 600 °C, respectively. The Hg-OM+ combined with aromatic clusters in EG 2 is difficult to decompose during pyrolysis process, it mainly released in the temperature range of 400–800 °C. Except the Hg-OM+ combined with aromatic clusters in EG 2 , >95% of Hg can be released before 600 °C for other samples. When the heating rate increased from 5 °C/min to 20 °C/min, the Hg releasing peaks ranged from 150 to 400 °C shifted gradually to higher temperature zones, but there was no obvious change in the positions of peaks ranged from 400 to 800 °C. Graphical abstract Unlabelled Image Highlights • The Hg distribution and releasing behavior in samples were investigated by using multistep solvent extraction method. • The Hg contents in EG 1 to EG 4 samples have little correlation with the total sulfur contents. • The Hg species and their thermal stability in different samples are quite distinct. • More than 95% of Hg in raw coal can be released before 600 °C. • The Hg-OM+ combined with aromatic clusters in EG 2 has higher releasing temperature than other Hg species. [ABSTRACT FROM AUTHOR]

Volatile compositions of coals during fast pyrolysis are principally governed by their bond structures and establishing the relationships between them is vital for deep understanding the pyrolysis mechanism. The structural features and bond information of Jining bituminous coal (JBC) were evaluated first by the combined advanced analytical tools. Subsequently, thermogravimetry coupled with pyrolysis-gas chromatography/time of flight mass spectrometry analysis were used to capture pyrolysis behavior and volatile species of JBC. The results showed that C O bond containing species were rich in JBC and mainly in the form of aryl ethers. Therefore, phenolic compounds were the most abundant species in volatiles during fast pyrolysis and C 6 C 9 phenols were the major constituent of this group. Average number of aromatic rings per cluster, number of substituents on each aromatic ring, and length of methylene chain in JBC were 3, 3–4, and 1.36, respectively. However, the three parameters calculated from the aryl-containing species in volatiles were all smaller than those of JBC. Cleavages of C al O, C al C al , C ar C al , and C ar O greatly contributed to volatile release and 67% of the mass loss during pyrolysis of JBC was caused by breakage of aliphatic C C and C H. Furthermore, pyrrolic nitrogen was found to be the most abundant form of organically bound nitrogen, but the pyrolysis volatiles contained more pyridine-N. [ABSTRACT FROM AUTHOR]

To establish the potential of thermally pretreated biomass as fuel for coal replacement in applications such as gasification, the fuel properties (higher heating value, elemental and proximate analyses) and the composition of char devolatilization products were analyzed and compared to those of sub-bituminous coal. Samples of pine, bamboo, corn cob and corn stover were pretreated at 250, 300, 350 and 400 °C with a hold time of 30 min. The devolatilization experiments were done in a Thermogravimetric analyzer, while captured volatiles were analyzed by thermal desorption/gas chromatography–mass spectrometry. The results showed that an increase in pretreatment temperature consistently decreased the oxygen and volatile matter contents of the char, while its fixed carbon content and the higher heating values increased, with a more drastic evolution from 300 °C onwards. Analysis of the char devolatilization products confirmed a major modification of the polysaccharides structure, as only traces of depolymerisation products were observed following pretreatment at 350 °C. Devolatilization of chars pretreated at 350 and 400 °C resulted in the evolution of the tar precursors, especially the phenolics, at similar and lower amounts, respectively, in comparison to coal devolatilization. Overall, a pretreatment temperature of at least 350 °C would be recommended for sub-bituminous coal substitution in gasification, while 400 °C could be considered for biomass species with high lignin content. [ABSTRACT FROM AUTHOR]

Hydrothermal carbonisation (HTC) is an attractive biomass pre-treatment as it produces a coal-like fuel, can easily process wet biomass and wastes, and lowers the risk of slagging and fouling in pulverised fuel (PF) combustion boilers. One of the major factors in determining the suitability of a fuel as a coal replacement for PF combustion is matching the char reactivity and volatile matter content to that of coals, as these significantly affect heat release and flame stability. The char reactivity of wood and olive cake biocoals and their respective drop tube furnace chars have been studied using thermogravimetric analysis in comparison to other biomass fuels and high-volatile bituminous coal. It was found that HTC reduces the reactivity of biomass, and in the case of HTC of wood pellets the resulting biocoal has a char reactivity similar to that of high-volatile bituminous coal. Proximate analysis, X-ray fluorescence analysis, and textural characterisation were used to show that this effect is caused primarily by removal of catalytic alkali and alkaline earth metals. Subsequent torrefaction of the wood biocoals was performed to tailor their volatile matter content to match that of sub-bituminous and high volatile bituminous coals without major impact on char reactivity. [ABSTRACT FROM AUTHOR]

Experimental and numerical investigations of the combustion of 2 bituminous coals under air, oxygen-enriched and oxy-fuel combustion conditions have been performed. 7 pulverized coal jet flames have been stabilized using a specifically designed flat flame reactor (FFR) allowing industrial heating rates to be reproduced. The investigated reacting media have been fully characterized in terms of temperature fields, fuel residence time, devolatilization rates and concentration profiles of O 2 , CO 2 , CO, NO and SO 2 . Obtained data have then been compared with predictions derived from a chemical reactor network (CRN) modeling approach. This latter incorporates a detailed reaction mechanism the formulation of which has been defined by comparing the results obtained through the implementation of 3 different detailed gas-phase combustion reaction schemes. On the whole, obtained numerical results show a good agreement with experimental data. By analyzing the reaction paths relying on the CRN predictions, the present study allowed highlighting and further exploring the influence played by the combustion atmosphere on the chemical pathways leading to species like CO, NO, SO 2 or soot precursors. The main findings drawn through this work especially led to trace the increased CO concentrations measured under oxy-fuel combustion (OFC) to heightened HCO production and tar oxidation. Alternative NO formation pathways arising under OFC conditions (like the HCN → HNCO → NH → NO and HCN → NCO → HNCO → HNO → NO routes) have, moreover, been highlighted. While the SO 2 production has been found to mainly depend on the quantity of fuel-S emitted during the devolatilization and on the local oxygen partial pressure (the main SO 2 formation pathway being indeed not truly affected by the nature of the combustion atmosphere), the analysis of the main routes involved in the oxidation of aromatics such as benzene, naphthalene and phenanthrene has been found well insightful in order to explain some reduced soot productions recently reported in the literature under OFC. [ABSTRACT FROM AUTHOR]

High-temperature rheometry and 1 H nuclear magnetic resonance (NMR) are two complementary techniques that have been used to investigate fluidity development quantitatively in the <53  μ m and 53–212  μ m size fractions of high ash Indian non-coking coals and imported non-coking, medium coking and good coking coals. It was found for the 53–212  μ m size fraction of the Indian bituminous coal with higher ash content (30 wt%) that, despite its high complex viscosity (>10 5  Pa·s), the maximum concentration of fluid H was quite similar to that of the good coking coal (40%). This Indian non-coking coal developed fluid H with the highest mobility (T 2L  > 150  μ s) in the coal series, regardless of the particle size fraction studied. The probable explanation for this abnormal behavior is that the mineral matter prevents bulk movement in the sample but the local mobility of the fluid phase is still high on the nanometer scale. Blending the two Indian non-coking coals with the highly fluid medium coking coal gave higher viscosities (i.e. lower fluidity) than predicted by the polymer blend rule, probably again due to the high mineral matter restricting bulk flow. This negative effect was less pronounced with the higher ash coal suggesting that the high mobility of the fluid entities in this coal might prevent the destruction of fluid entities evolving from the medium coking coal. Partial demineralization of the high ash Indian non-coking coal to 17 wt% through a sink-float method did not decrease the complex viscosity of this coal but reduced the maximum mobility of the fluid H to levels observed with the lower ash content (20 wt%) Indian coal. Therefore, this reduction in mobility could be directly related to the mineral matter in the Indian non-coking coal. [ABSTRACT FROM AUTHOR]

Direct liquefaction of Chinese Hami sub-bituminous coal was conducted with binary mixtures of hydrogen donor solvent tetralin (THN) and non-donor 1-methylnaphthalene (1-MN) or naphthalene (Nap.). Effects of solvent composition, temperature, atmosphere, and catalyst FeS 2 on product distribution and hydrogen consumption were investigated at solvent/coal mass ratio of 2. The results show that oil yield increases from 47.70% to 59.95% with 1-MN/THN ratio changing from 2:1 to 1:2. Hydrogen donating ability of binary solvents increases with the rising ratio of THN. H 2 contributes noticeably positive effect on coal conversion in the case of liquefaction with insufficient hydrogen donor solvent. Oil yield obtained during direct coal liquefaction (DCL) with Nap./THN is 58.32%, which is 10.62% higher than that with 1-MN/THN at same solvent ratio of 2:1. This is owing to demethylation effect of 1-MN under liquefaction condition. 1-MN demethylation is induced by active hydrogen and coal radicals, and could consume noticeable hydrogen during DCL. This indicates that the amount of alkylarenes included in liquefaction mixed solvents should be limited, or sufficient hydrogen donor solvent is required to achieve high coal conversion. [ABSTRACT FROM AUTHOR]

This paper has addressed the techno-economic feasibility regarding the selective removal of sodium (Na) and calcium (Ca) from low-rank sub-bituminous coal, aiming to reduce the ash slagging and fouling propensity in the pulverized coal-fired boilers. Four novel process integrations were proposed and simulated in Aspen Plus. Both the novel counter-current three-stage water washing process and an acid-water two-stage washing process have proven to improve the ash fusion temperature satisfactorily, reducing the mass fraction of Na 2 O in ash from 4.32 wt% to 0.85 and 0.19 wt%, respectively. In addition, the use of acid-water washing removed 12.5% CaO and 19.5 wt% total ash. For the recycle and treatment of wastewater, the water gain is desirable for the use of an evaporator, owing to the dewatering of the initially high-moisture coal (25 wt%) in the centrifugal and the high water recovery rate from the evaporator. However, the good performance of evaporator was counteracted by the considerable capital cost caused by the huge heat transfer area requirement. Instead, the use of reverse osmosis (RO) resulted in a water loss up to 228.4 kg/t coal. Additionally, prior to the RO treatment unit, the recycle and reuse of the unsaturated water for maximum six times and four times for three-stage water washing and acid-water two-stage washing, respectively, was critical in reducing both the water and power consumption. The water consumption dropped to 38.1 kg/t coal and 48.1 kg/t coal for the three-stage water washing and acid-water two-stage washing process, respectively. Both are remarkably lower than 85.0 kg-water/t black coal. In terms of the power consumption, it decreased to ~ 9.4 kWh/t coal for the three-stage water washing process and further down to 5.8 kWh/t for the acid-water washing case, which was even slightly lower than 6.3 kWh/t for the black coal. Furthermore, the integration of acid-water washing and RO was also demonstrated to be economically viable by its high NPV, IRR and short payback period. Sensitivity analysis indicate that, the original Na content in raw coal is the most influential variable on the water and power consumption of the overall process, followed by the initial moisture content in the raw coal. For a low-rank coal containing > 2150–2520 ppm Na and/or < 19 wt% moisture, the washing process proposed would turn economically unviable compared to the existing black coal washing process. A minimum selling price of 136 RMB/t (− 32% deviation) was also necessary to keep both NPV and IRR positive as well as the payback period shorter than the project lifetime. [ABSTRACT FROM AUTHOR]

An earth-abundant and low cost bituminous coal was used as precursor to prepare synthetic graphite materials through preliminary carbonization coupled with further high temperature graphitization treatment at 2000–2800 °C. The microstructure characteristics of the obtained synthetic graphite materials were characterized by means of X-ray diffraction, scanning electron microscope, transmission electron microscope, Raman spectroscopy and nitrogen adsorption–desorption. The results show that the microstructures of synthetic graphite materials are strongly dependent on the graphitization temperature. The synthetic graphite graphitized at 2800 °C has perfect ordered layered structure with high graphitization degree and relatively large surface area with well-developed mesopores, which offers a favorable pathway for the electrochemical intercalation-deintercalation of lithium ions in carbon matrix. Such synthetic graphite applied as anode materials for lithium-ion batteries presents a maximum reversible capacity of 310.3 mAh·g − 1 at current rate of 0.1C and still remains as high as 143.9 mAh·g − 1 at current rate of 5C. Moreover, the synthetic graphite also exhibits superior rate capability and outstanding cycling performance with over 95.3% initial capacity retention after 100 cycles. This study demonstrates a promising feasibility for large-scale production of synthetic graphite materials from bituminous coal for high performance lithium-ion batteries. [ABSTRACT FROM AUTHOR]

A dual loop gasification (DLG) system consisting of three separated reactors and two bed material circulation loops has been proposed for steam gasification of low-rank coal to obtain hydrogen-rich gas with low tar content. The system decouples the gasification process into fuel gasification, tar destruction and residual char combustion, which occur in three independent reactors correspondingly, i.e. a gasifier, a reformer and a combustor. Both the gasifier and the reformer are separately interconnected with the single combustor, forming two bed material circulation loops in parallel. In this way, both the gasifier and the reformer could be operated individually under optimized conditions. With Shenmu bituminous coal as feedstock and calcined olivine as both solid heat carrier and in-situ tar destruction catalyst, the performance of the system for the steam gasification of the coal has been investigated. It has been found that the tar was effectively removed under higher reformer temperature and in the presence of the olivine catalyst, and the coal gasification was promoted at higher gasifier temperature, S/C and ER. [ABSTRACT FROM AUTHOR]

The impact of residence time and temperature during hydrothermal carbonization (HTC) on hydrochar properties and CO 2 gasification properties has been studied for brewers' spent grain (BSG), treated at temperatures from 180 °C to 280 °C and residence times from 0.5 to 12 hours. Lower heating values (LHV) of the hydrochars are found to increase to values of bituminous coal and anthracite as reaction severity increases. Temperature is found to have a greater influence on the LHV of the hydrochar than residence time. Mass and energy yields decrease with increasing reaction severity. With higher reaction severity decreased molar O/C and H/C ratios as well as decreased volatile contents and increased fixed carbon contents are observed. The influence of residence time is more pronounced for the formation of fixed carbon, main carbonization reactions occur for a reaction severity greater than 180 °C and 0.5 hours. Char reactivity is found to decrease with increasing carbonization reaction severity with a strong influence of both residence time and temperature due to the formation of fixed carbon in the hydrochar. Activation energies are decreased with increased carbonization temperature but only mildly affected by residence time. Hereby the catalytic influence of ash compounds has to be further determined. [ABSTRACT FROM AUTHOR]

Two Cl-free refuse plastic and paper fuels (RPFs) produced by hydrothermal treatment with Ca(OH) 2 , as well as two biomasses, were co-fired with bituminous coal in a lab-scale drop tube furnace (DTF). The results indicate that the addition of biomass and RPF partially reduced the emission of SO 2 , which can readily cause corrosion, deposition and pollution. For the biomass co-firing, the particulate matter (PM) emissions from the black pellet (BP) series were 5.0% higher than those from the white pellet (WP) series because more sticky particles were formed with the increment of Ca-Al-Si and K-Al-Si, which absorbed alkali vapor and fine grains in the gas bulk to inhibit the PM emissions. For RPF, the major origins of sticky particles turned into Ca-Al-Si and Ca-K-Al-Si, the proportion of which was dramatically higher than that from the biomass, resulting in a stiffer suppression of PM formation. In general, the promotion of Ca from additives conversely restrained its transformation into PMs during both biomass and RPF co-firing. It can be concluded that the co-firing of RPF with bituminous coal provides an alternative approach to simultaneously control the emissions of greenhouse gases, gaseous pollutants and PM while remediating plastic waste. [Display omitted] • Co-firing of bituminous coal with RPF and biomass was investigated. • Ca transformation during co-firing dominated the formation of PMs. • The CCSEM + FactSage method can be applied to RPF. • The formation of sticky particles was predominantly influenced by M-Al-Si. • The addition of high-plastic fuel (HPF) reduced the emissions of SO 2 and PM. [ABSTRACT FROM AUTHOR]

Five different blends of Utah bituminous coal and steam-exploded pine (100/0, 75/25, 50/50, 25/75, 0/100 by mass) were fired in a 1.5 MW th combustor. Primary objectives were to understand mineral matter behavior by analyzing aerosol size distribution, aerosol size-segregated composition, ash deposition mass, and ash composition. For particle size <0.1 μm, pure coal had the lowest aerosol concentration and pure biomass showed the highest (higher nucleation of potassium salts), a trend which reversed for particles >0.1 μm. During pure biomass combustion, aerosol particles >15 μm contained higher mass fractions of potassium (+126%), calcium (+132%), and iron (+115%) and lower fractions of aluminum (−49%) and silicon (−29%) than pure coal. Ash deposition mass decreased with increasing biomass blends. Downstream ash deposits contained −3% to 55% higher sodium and potassium than the upstream ash, which highlights the dilution effect of the condensation layer by inertial impaction on the upstream side. Submicron ash load and deposited mass for 30-min and 90-min tests showed R2 values of 0.974 and 0.966, indicating that smaller particles' concentration determines the final mass. The results suggest that plant operators should not face any difficulties while co-firing these blends with respect to ash deposition by fouling. [Display omitted] • Biomass-coal blends were co-fired to analyze the ash aerosol and deposition behavior. • Ash aerosol load and ash deposit mass decreased with increase in biomass blend ratio. • Biomass aerosol contained higher K, Ca, and Fe and lower Si and Al than coal aerosol. • Submicron ash load indicated a high correlation with final ash deposition mass. • Downstream ash deposits had a higher mass fraction of Na and K than upstream ash. [ABSTRACT FROM AUTHOR]

The effects of mechanical activation on the co-liquefaction of Xigou sub-bituminous coal (XSBC) and a mixture solvent of creosote oil and Karamay petroleum vacuum residues were investigated. The structure of the mechanically activated coal was more porous than the structure of XSBC according to the characterization results. Compared to XSBC, the average pore size of the activated coal increased by 106.7%, whereas the specific surface area decreased by 74.7%. The absorption peaks of OH at 3300 cm − 1 and C O at 1720–1650 cm − 1 decreased. The ratio of the fractions of aromatic carbon and sp 2 -hybridized carbon decreased by 13%. The mass loss from 100 °C to 300 °C increased by 237% and the apparent activation energy in the liquefaction temperature range of 300–400 °C decreased by 21.6%. The yields of total oil, asphaltene and preasphaltene (A + PA), gas and residue of mechanical activated coal slurry were 82.67, 10.80, 4.12 and 2.40%, respectively. Compared to raw coal slurry, the total oil yield and the gas yield of activated coal slurry increased by 8.2 and 63.5%, respectively, whereas the A + PA yield and the residue yield decreased by 29.9 and 57.5%, respectively. The H 2 consumption decreased by 19.9%. Moreover, the yield of heavy oil and distillate in the liquefied product decreased by 51.1 and 31.3%, respectively, whereas the yields of gasoline and diesel increased by 65.5 and 10.7%, respectively. [ABSTRACT FROM AUTHOR]

Preheating stage of direct liquefaction of Yunnan lignite (YN) and Hami sub-bituminous coal (HM) in tetralin at temperature range of 200–350 °C was investigated under nitrogen atmosphere. In order to reveal the product characteristics and hydrogen transfer between coal and solvent during preheating process, thermo-gravimetric analyzer coupled with mass spectrometer (TG–MS), X-ray photoelectron spectroscopy (XPS) and gas chromatography coupled with mass spectrometer (GC–MS) were employed. The results show that yields of light products, i.e., oil, gas, and water, increase with raising temperature during the preheating process. YN and HM achieve 51.69% and 44.19% (daf) light products yields at 350 °C, respectively. Moreover, oxygen-containing functional groups, such as carboxyl, ethers, and alcohols in raw coal are reduced after preheating. In addition, hydrogen transfer achieves a perceptible extent even at 200 °C and the amount of transferred hydrogen increases with raising temperature. A positive dependence of hydrogen transfer on conversion is observed during preheating stage. Comparing the two coal samples, YN obtains higher conversion and hydrogen transfer due to its higher thermal reactivity at this temperature range. However, HM achieves higher oil yield than YN does at 350 °C since high hydrogen transfer amount and H/C ratio of raw coal promote the oil yield. [ABSTRACT FROM AUTHOR]

Although considerable progress has been made in revealing the coal macromolecular structure via solvent extraction, there remains a challenge in elucidating the coal structure due to low extraction yields of coal, poor selectivity of extraction solvents, and complexity of extracts. In this work, a high-volatile bituminous coal was successfully separated into seven groups (G 1 –G 7 ) with less diversity within each class using multistep extraction followed by column chromatography. The total extraction yield (dmmf) reached up to 56% and the structural characteristics of the seven groups were identified and investigated with a series of analytical techniques. The results showed that the individual groups had a rather unique composition and their chemical properties were different in elemental composition, functional groups, aromatic cluster size, number and length of the alkyl side chains, and degree of order, which resulted in differences of their pyrolysis reactivities. Aliphatic hydrogen accounted for 99% of total hydrogen in n -heptane eluted fraction (G 4 ) but the aliphatic degree in the extract residue (G 1 ) was only 35.7%. The ratios of aromatic bridgehead carbon were 0.32, 0.30, and 0.27 for G 1 , CCl 4 insoluble fraction (G 2 ), and n -heptane insoluble fraction (G 3 ), respectively. Additionally, total volatiles achieved 99.8, 98.1, 98.2, 89.0, and 60.0%, respectively during pyrolysis of G 4 , toluene eluted fraction (G 5 ), ethyl acetate eluted fraction (G 5 ), methanol eluted fraction (G 7 ), and G 3 at end temperature of 800 °C, which were substantially higher than those for G 1 and G 2 . In comparison with the partition of coal structure using maceral components, the proposed separation method provides an efficient and convenient investigating for structural exploration and these data can be combined to create structures that are cognitive of the structural diversity present. Through this, exploration of the complex conversion mechanism of coals would become more accessible during pyrolysis, gasification, liquefaction, and coking processes. [ABSTRACT FROM AUTHOR]

The chemical components of ash in coal are important factors affecting the ash deposition in the entrained-flow gasification process. Most previous research aimed at investigating pertinent chemical components affecting ash deposition has focused on the deposited sample after experiments without consideration of the time frame to verify the relationship between ash chemical components and deposition. However, this study examined the relation of the chemical components to the ash deposition by using the drop tube furnace (DTF), in which a real-time weight measurement (RWM) system had been installed. The RWM system, capable of recording the amount of deposited ash per second, was specifically developed for this work. Three pulverized coal samples, in the range of bituminous and sub-bituminous coal, were employed in the DTF experiments to compare the relationship between the ash chemical components and deposition. It was found that the ash deposition behavior in a real-time was related to the presence of Fe and Ca components, and high concentrations of these components tended to increase the deposition rate. The ash deposition could be diverse by maintaining or decreasing the Fe and Ca components, which are responsible for fouling growth. [ABSTRACT FROM AUTHOR]

Coal is a major source of energy. In order to overcome the operational problems and environmental issues related to direct utilization of coal, coal upgrading research and development works are in progress in terms of moisture removal, demineralization, removal of harmful constituents such as sulfur, mercury etc. There have been two major approaches to achieve this: dissolving minerals out of coal – the product is termed as ultra clean coal (UCC) and solvent extraction of coaly matter – the product termed as ash-free coal (AFC). In this paper, current knowledge regarding chemical upgrading of coal has been reviewed. In particular, production process and effects of various parameters on yield and product quality have been discussed. The potential applications of the demineralized coals and the economic assessment with respect to commercialization of this process have also been presented. Chemical treatment processes have been demonstrated as the most effective techniques for removal of ash forming minerals from coal to produce coal with minimal or almost no ash. In general, the ash content of UCC is reported within the range of 0.15 to 0.6% either by treating bituminous coal with HF followed by HCl or HNO 3 . Most effective treatment available in literature is HF followed by HNO 3, achieving ash content as low as 0.15%. Organic solvents like polar, non-polar and mixed solvent have been used to extract the organic matters from coal to produce AFC. In general, extraction yield has been found higher at high treatment temperature with polar solvents. The advantages of using UCC and AFC are that they emit lesser pollutants and cause less or no abrasion/erosion and fouling/slagging in the boilers. However, the literature on economic evaluation of AFC applications is scarce and needs to be carried out in future. [ABSTRACT FROM AUTHOR]

Oxy-fuel combustion of single coarse sub-bituminous coal char particle is investigated in an isothermal mass loss apparatus. Experimental studies are performed at the reactor temperature of 1100 K and in varying O 2 concentrations of 42–60% in both O 2 -CO 2 and O 2 -N 2 environments. A fully transient model is developed for the combustion and gasification reactions including the transport of heat and mass in the porous char particle and the gas film. The model is validated with experimental findings of the present authors as well as that reported in literature over a wide range of O 2 concentrations. Simulation study is carried out to assess the effect of the particle size, the reactor temperature and the gas composition. The simulation shows that low diffusivity of O 2 within the reactor in CO 2 environment and the endothermic gasification reaction are mainly responsible for lowering the peak temperature and the rate of combustion of char than that in O 2 -N 2 environment. It is also observed that though the effect of CO 2 on the combustion rate at low temperatures is insignificant, it is considerable at the reactor temperature of 1273 K and above in O 2 -CO 2 environment. The model is expected to provide vital information for reactor design under oxy-fuel combustion and its integration with CFD analysis for identifying the optimum particle size, reactor temperature and oxygen concentration. [ABSTRACT FROM AUTHOR]

Solvent extraction of coals has been practiced extensively for various purposes including the determination of coal structure. It is generally assumed that the extraction is mainly a physical process involving little change in covalent bonds. But different opinions were reported. This work studies the behavior of radicals during extraction of 3 low rank bituminous coals using 5 solvents, including hexane, toluene, tetrahydrofuran (THF), 1,2,3,4-tetrahydronaphthalene (THN), and N -methyl-2-pyrrolidinone (NMP), using electron spin resonance (ESR). The extractions are carried out at temperatures from the ambient temperature to temperatures somewhat higher than the boiling points of the solvents, as well as under ultrasound. It is found that the radical concentration of the coals changes during the extraction, and the change is influenced by temperature and varies with the solvent. The decrease in radical concentration in most solvents at temperatures lower than their boiling points is attribute to coupling of free radicals dissolved from the coals, while the increase in radical concentration at high temperatures and in NMP is attributed to the cleavage of weak bonds in coals by the solvents. [ABSTRACT FROM AUTHOR]

To better understand coal performance during underground coal gasification, coal combustion and in-situ enhancement of coalbed methane recovery by heating, the variable gases generation and pore structure of subbituminous coal and bituminous coal with thermal treatment related to organic petrology are investigated. Multiple experiments including organic petrology analysis from an optical microscope, gases analysis from thermogravimetry coupled with mass spectrometry (TG-MS), pore structure analysis using scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP) and nuclear magnetic resonance (NMR) were constructed to simulate the thermal treatment of coal at elevated temperatures. The coal petrology results exhibit that the submacerals that contribute to the gases generation were significantly reduced when temperature was over 400 °C, especially for collinite, cutinite, resinite and telalginite. And there was only a slight difference in CO 2 content between subbituminous coal and bituminous coal, which was reduced in the bituminous coal. On the other hand, thermal decomposition of functional groups of submacerals at over 400 °C also creates more seepage pores and fractures. Pore structure analysis indicates that the adsorption pores were observed with aggregates of plate-like particles leading to slit-shaped pores below 200 °C. However, the massive seepage pores and fissures (over 35.42% in volume) were created in the high-temperature-treated coals, especially between 400 °C and 600 °C. Furthermore, the dominant seepage pores and fissures formed at high temperature (> 400 °C) are due to the pyrolysis of semifusinite and collinite submacerals. These investigations may serve to characterize gases generation and pore evolution of coal during thermal treatment. [ABSTRACT FROM AUTHOR]

Vitrinite-rich concentrates were produced using a float-sink technique from five single-rank Chinese bituminous coals with R random ranging from 0.88% to 1.73%. The non-isothermal thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) of these concentrates were carried out simultaneously at the heating rate of 8 °C/min from 50 °C to 1200 °C, and the determination of the caking index ( G ) was also performed. The TGA results demonstrate that the devolatilization is divided into three regions and there are not explicit relationships between coal rank and characteristic parameters during the 300–900 °C region, such as DTG max , T max , and weight loss. The DSC results show that the heat of pyrolysis is comprised of three stages characterized by different heat flows and no explicit correlations between coal rank and heat flow as well as peak number in the range of 300–900 °C exist. In terms of the TGA and DSC results, the relationship between the caking index and characteristic parameters derived from the TGA and DSC curves is examined and developed to predict the caking index of single-rank bituminous coal. [ABSTRACT FROM AUTHOR]

The potential of achieving effective utilization for a given coal using maceral separation is dependent on the differences in thermal characteristics of its maceral concentrates. In this paper, vitrinite-rich and inertinite-rich concentrates were obtained from five bituminous coals with R random ranging from 0.64% to 1.73% using a float-sink procedure. The devolatilization characteristics and kinetics of maceral concentrates were investigated using thermogravimetric analysis at the heating rate of 8 °C/min − 1 from 50 °C to 1200 °C. The devolatilization is comprised of three regions characterized by different weight loss rates. During principal devolatilization, inertinite-rich concentrates are characterized by similar initial temperature, slight greater temperature of maximum rate of weight loss, and greater terminal temperature. The maximum rate of weight loss and the index of volatile matter released decrease with an increase in rank; the lower the rank, the greater the differences between vitrinite-rich and inertinite-rich concentrates. The principal devolatilization displays the greatest apparent activation energy, followed by post-principal devolatilization, and the least for initial devolatilization. During principal devolatilization, the apparent activation energy difference of vitrinite-rich and inertinite-rich concentrates is higher in lower-rank coal and becomes almost zero at the R random of 1.73%. The minimum activation energy and apparent activation energy were in detail discussed. [ABSTRACT FROM AUTHOR]

Extraction residue from Geting bituminous coal (ER GBC ) via ultrasonic extraction with isometric carbon disulfide/acetone binary solvent was subjected to thermal dissolution (TD), thermal dissolution under pressurized nitrogen (TDN), non-catalytic hydroconversion (NCHC), and catalytic hydroconversion (CHC) in cyclohexane at 300 °C for 3 h. The catalyst was prepared by thermally decomposing Fe(CO) 5 and Ni(CO) 4 onto γ-Al 2 O 3 . The reaction mixtures from TD, TDN, NCHC, and CHC were sequentially extracted with petroleum ether, carbon disulfide, methanol, acetone, and isometric acetone/carbon disulfide binary solvent to afford extracts 1–5 (E 1 –E 5 ). Detailed characterizations of the extracts were performed with a gas chromatography/mass spectrometer (GC/MS) and Fourier transform infrared spectrometer. The results show that the yields of E 1 and E 3 from CHC are appreciably higher than those from others, suggesting the great influence of CHC on the breakage of -CH 2 - and -O- linkages connected to condensed aromatic rings. According to analysis with GC/MS, alkanes and arenes are the most abundant species in each E 1 , in which most of the arenes are methylarenes. Arenols and phthalates are the predominant oxygen-containing organic compounds. Arenes with 1 or 2 ring(s) markedly increase by using H 2 , especially in the presence of the catalyst. The H . catalytically generated over FeNi–S/γ-Al 2 O 3 and the stabilizing effect of H 2 on the generated radicals could play crucial roles in cleaving bridged linkages connected to condensed aromatic rings and thereby enhance the yields of alkylarenes through NCHC and CHC. Related mechanisms for the formation of some species derived from NCHC and CHC of ER GBC are discussed. [ABSTRACT FROM AUTHOR]

Studies were conducted to develop the scientific basis for the use of low-grade solid hydrocarbons and biomass as starting fuel and an energy additive to the main fuel for coal-fired boilers. Char, softwood sawdust, brown and bituminous coals with a particle size of 140–250 μm were used in an air-dry state and after impregnation with rapeseed oil. Analytical studies included surface texture analysis of solid fuel particles, determination of their wetting properties with respect to water and rapeseed oil, thermogravimetric and calorimetric analyses, FTIR analysis of gaseous combustion products, analysis of the elemental composition and texture of the ash surface. Fuel combustion characteristics were studied in conditions of fine fuel particles movement in a heated air stream: 5 m/s, 500–800 °C. Impregnation of solid fuels with oil led to the moisture displacement from the pores of fine particles (oil content in various solid fuels 5.6–22.4%). It increased the combustion completeness of fine particles in a shorter period of time (the ignition delay time reduced by 15–30%) and the thermal effect of the exothermic reaction (by 2.2–18.1%). Oil vapors first ignited in the vicinity of the particle, thereby intensifying the combustion of solid component in fossil fuels. [Display omitted] • Impregnation of solid fuel with oil led to the moisture displacement from its pores. • Oil-impregnated fuels show reduced ignition delay time and increased thermal effect. • Oil-impregnated char is preferable for boiler start-up. • Adsorption properties of solid fuel and biomass affect the ignition delay. • Oil-agglomeration does not change the ash composition. [ABSTRACT FROM AUTHOR]

Ash deposits formed on an air-cooled probe at different temperatures during combustion of coal blends of a Zhundong lignite (ZL) and an Australian bituminous (AB) were studied in the present work. The blends with various AB ratios were combusted in a drop tube furnace in air at 1400 °C, and the ash deposits formed on the probe top surface maintained at 500 °C, 600 °C, 700 °C, and 750 °C, were collected and characterised using XRD and SEM-EDS for their mineralogy, morphology and elemental composition. The size distributions and sintering temperatures of the ash deposits were also determined. At the probe temperature of 500 °C, the ZL ash deposit was dominated by fluxing minerals where significant amounts of fine particles (< 10 μm) and their aggregates existed, leading to low ash sintering temperatures. As the AB ratio increased to 20 wt% and above, the amount of the fluxing minerals in the deposits decreased while the amount of refractory quartz and mullite minerals increased. Morphologically, the refractory ash particles from AB coal diluted the Na-bearing mineral phases and the contacts between fine ash particles, leading to the absence of nepheline and, correspondingly, an increase in the ash sintering temperature. In addition, as the probe temperature increased, mineral interactions and ash sintering were facilitated when the AB ratio was less than 20 wt%, leading to the formation of new mineral phases and an increase in ash particle sizes. However, no significant mineralogical and morphological changes were observed when the AB ratio was higher than 40 wt%, indicating that these ash deposits were more refractory and resistant to the temperature change. [ABSTRACT FROM AUTHOR]

Coal combustion introduces large amounts of pollutants into the atmosphere, including trace elements originally bonded in the coal matrix. The emission of these elements raises considerable environmental and human health concerns. To optimise process parameters and reduce gaseous trace element emissions, it is of significant importance to investigate the solid–gas partitioning behaviour of trace elements during combustion processes. To date, limited numbers of experimental studies have been carried out, especially using pilot circulating fluidised bed (CFB) combustion plants. This paper discusses the partitioning behaviour of seven elements (As, Ba, Cd, Cr, Cu, Mn and Pb) in different product streams during combustion tests on anthracite and bituminous coal. The combustion tests were carried out in a 2.5 MW th CFB unit equipped with multi-stage control of solids, which is well suited for trace element partitioning studies. The mass balance ratio of the elements studied ranged from 56%–137%, which is, considering their concentrations, both satisfactory and reasonable. Most of the elements were found in the bottom ash and fly ash during CFB combustion, while small amounts of As, Cd and Pb were emitted to the atmosphere along with fine particulates. The trace elements are more likely to be retained in the bottom ash from the bituminous coal but not in the case of anthracite. For the volatile elements, the enrichment in solid streams follows the trend of: bag filter ash > cyclone ash > IBHX (in-bed heat exchanger) solids > bottom ash, indicating that the volatile elements tend to be enriched in fine particles. Anthracite, when compared to bituminous coal, shows lower emission factors for all monitored elements, except for Pb. This study can serve as a good reference for trace element control strategies in coal-fired CFB boilers. [ABSTRACT FROM AUTHOR]

Fluidized bed co-combustion of raw paper sludge (Raw-PS) and hydrothermally treated paper sludge (HTT-PS) with either low (Lo-Coal) or high reactivity coal (Hi-Coal) was investigated. The paper sludge was treated in a pilot-scale hydrothermal reactor at 197 °C and 1.9 MPa for 30 min. South African bituminous and Thai subbituminous coals were selected as representative of Lo-Coal and Hi-Coal, respectively. A 110-mm bubbling fluidized bed combustor was used in this study. During the steady combustion tests the nominal temperature was 858 °C, the fluidization velocity was 0.5 m/s, and the excess air was varied as 20%, 40%, and 60%. Both single fuel combustion and co-combustion were tested. Co-combustion tests were conducted by feeding the sludge at mixing ratios of 30% and 50% (mass basis) with coal. The main focus of this study was on NO x emissions and unburned carbon performance. Results showed that at 30% mixing ratio using HTT-PS instead of Raw-PS could reduce NO x emission by 3–6% and 9–17% in the case of Lo-Coal and Hi-Coal, respectively, and the loss of unburned carbon could be decreased by 15–18% and 36–53% for Lo-Coal and Hi-Coal, respectively. The particle size distribution of fly ash of all samples was similar regardless of the excess air variation. On the whole, the hydrothermally treated paper sludge showed better performance for co-combustion with coal and would be a better choice compared to the original raw paper sludge. [ABSTRACT FROM AUTHOR]

The purpose of this work is first to investigate the slurryability of two chars produced from the rapid hydrogasification of two bituminous coals (YY coal and FG coal) in a pilot-scale entrained flow gasifier (abbreviated as RH char). Results showed that both RH chars had very poor slurryability mainly owing to the microporous and capillary structures of particles and the high water holding capacity, in sharp contrast to the properties of the parent coals and the char obtained from a common slow pyrolysis. The work thereafter aims at making a commercially usable water slurry by using the blends of RH char and YY coal. The slurry containing an adjusted solid blend of 60% total solid weight loading with 0.5% naphthalene sulfonate formaldehyde dispersant showed all satisfactory performances in the apparent viscosity, fluidity and static dispersion stability. Furthermore, it was found that the slurryability could be improved by an interactive effect between RH char and raw coal, which depended on the blending pairs and blending proportions. [ABSTRACT FROM AUTHOR]

Oxy-combustion is a promising technology to enable the capture of CO 2 from power plants based on diverse raw material. This paper describes and compares the results of technical and economic viability studies of a 15 MW power plant based on a corn-rape blend oxy-combustion, a bituminous coal-combustion and a bituminous coal oxy-combustion located in the north of Spain. Technical simulations were implemented in Aspen Plus© software. The economic viability studies were based on the typical economic indicators such as net present value, rate of return, specific total plant investment, cost of electricity, cost of CO 2 avoided and energy consumption for CO 2 avoided. A sensitivity analysis was carried out in order to identify the most important factors affecting the investment risks. The use of a cryogenic air separation unit was associated with a reduction in oxy-combustion plant viability. While coal-combustion process reported an enough profitability, a supplementary public grant of 63 €/MWh and 57 €/MWh were required in coal oxy-combustion process and biomass oxy-combustion process respectively to obtain a positive profitability. A stability of raw material and electricity markets was found to be necessary to improve a risk reduction for the potential investment. [ABSTRACT FROM AUTHOR]

Fouling and slagging depend upon the boiler and firing system design, operational parameters and fuel properties. Release of inorganic compounds during combustion and their transformation into critical gaseous species, aerosols and ash particles may substantially affect the boiler efficiency and availability, due to the formation of fireside deposits. The composition of the mineral matter in three bituminous coals and the associated deposits formed at the inlet of the superheater level in a 730 MW th pulverized fuel boiler are discussed in this paper. A cooled probe was used to investigate the initial layer of the deposits while an uncooled probe was used to investigate the outer layer. In all initial layers, spherical (formerly molten) iron-rich particles, likely derived from pyrite were observed. Moreover, particles in the initial layers and mineral phases of the coal samples were determined quantitatively. Based on these analyses thermo-chemical equilibrium calculations were performed using the FACT-Sage simulation software to identify the effect of reducing and oxidizing flue gas atmospheres on the ash melting behavior and to assess their importance on the build-up of the initial deposit layers. The results of this work indicate that the deposition of an ash particle is strongly influenced by the particle's history. Besides its composition, in particular, temperature, and the atmosphere that a particle passes through have a significant influence on the mineral transformation and the adhesion of the particle. [ABSTRACT FROM AUTHOR]

The DTE Power Plant includes four boilers, each generating up to 5.7 million lbs/h of supercritical steam, and each supporting the generation of up to 800 MW e (net) of electricity. At the time of the testing two units were equipped with both scrubber and selective catalytic reduction systems in addition to electrostatic precipitators. Over a two year period, the Plant modeled and tested a wide variety of fuels and fuel combinations with a base fuel of Wyoming Powder River Basin (PRB) subbituminous coal and Central Appalachian bituminous coal. Fuels incorporated into the blend included petroleum coke, northern PRB subbituminous coal, and northern Appalachian bituminous coal. Various blend combinations were considered and/or tested. Operation with 100% PRB was also tested. The objective was to optimize the fuel blend from both technical and economic perspectives. The blend proven to be optimal from both technical and economic perspectives included 10% petroleum coke with PRB coal and, as necessary, Central Appalachian coal. This blend was implemented. [ABSTRACT FROM AUTHOR]

Steam co-gasification of pine sawdust and bituminous coal was conducted in a lab-scale external circulating radial-flow moving bed (ECRMB) gasification system. The system is composed of three decoupled reactors, i.e., a gas–solid countercurrent moving bed pyrolyzer, a radial-flow moving bed gasifier and a riser-type combustor. Calcined olivine was used as circulating heat carrier and in-situ tar destruction catalyst as well. The influences of biomass blending ratio (BR), pyrolyzer temperature, gasifier temperature and steam to carbon mass ratio (S/C) on the gasification performance were investigated. The results indicated that the gas and tar yields increased with the increase of BR. Synergetic effect based on gas composition was found during co-gasification. At the S/C range of 0 to 1.3, the gas yield and H 2 content in product gas increased but CO 2 decreased with the increase of S/C. Higher gasifier temperature promoted the gas yield, H 2 + CO in product gas, carbon conversion and chemical efficiency of the process. A gas yield of 0.60 Nm 3 /kg daf and a tar yield of 5.8 g/Nm 3 in the gas were obtained at the gasifier temperature of 850 °C, BR of 50% and S/C of 1.3. Pyrolyzer temperature at the range of 500 to 700 °C had no remarkable influence on the product gas composition. [ABSTRACT FROM AUTHOR]

Hydrothermal treatment of coal was carried out in a lab autoclave at 533 K for 30 min and coal pyrolysis was completed in a tube reactor at 873 K for 15 min with the heating rate of 5 K/min. The thermal analysis of the raw and treated coal was compared by thermogravimetric analyzer. The distribution of carbon in coal was detected by solid state 13 C nuclear magnetic resonance. The free radical concentrations in coal were determined by electron paramagnetic resonance spectrometer. The results show that hydrothermal treatment is an effective method for upgrading and deoxygenation of low rank coal. The pyrolysis water yields decrease from 9.21 wt.% of the raw brown coal to 7.40 wt.% of the treated brown coal. The pyrolysis tar raises about 18% for the treated brown coal and 5% for the treated sub-bituminous. After hydrothermal treatment, the treated coal has lower contents of oxygen functional group and higher percentage of alkyl carbons in comparison with the raw coal, the free radical concentrations in treated coal increase, especially for brown coal, which is the result in the increment of tar yield. [ABSTRACT FROM AUTHOR]

The combustion behavior of biomass as a fuel varies dependent on source of the raw material, but also on the type of pre-treatment. In this work steam exploded and torrefied woody biomass were studied with respect to NO x formation in co-firing experiments. Most of the reported data is based on small scale experiments and simulations. In this work, however, have three different cases been investigated experimentally in a 1.5MW th combustor supported by reaction simulations. One case corresponds to firing 100% Utah bituminous coal and two cases where 15% of the coal (on a mass basis) has been replaced with either torrefied or steam exploded biomass. Two of the cases was also studied in a utility scale 1.3 GW th industrial boiler. In both units did the case with pure coal result in the highest amount of NO formed, which was expected due to the higher amount of fuel-bound nitrogen in the coal, as compared to the biomass fuels. The fuel analyses indicate that the nitrogen content is the same in the two investigated biofuels. However, the amount of NO formed differed. Gas composition measurements reveal that the partitioning of volatile nitrogen species (HCN and NH 3) varies between the biomass co-firing cases. This was investigated further using detailed reaction simulations and is suggested as the main reason for the observed difference in NO formation. • Co-combustion of coal and biomass in a 1.3 GW th power plant. • The choice of biomass pre-treatment method has an influence on the NO X formation. • In-flame mapping of nitrogen species using. • The effect of co-combustion on NO formation depends on the overall conditions. [ABSTRACT FROM AUTHOR]

This study evaluated the effect of primary air velocity (PAV) on the ignition characteristics of bituminous coal and semicoke mixture (1:1, wt%) in a reducing-to-oxidizing environment (R-O) in a 300-kW pilot-scale furnace that characterized the ignition behaviors of pulverized coal (PC) furnaces. The early ignition characteristics of the primary combustion zone (PCZ), including ignition distance, ignition mode, flame stability and kinetic parameters, were studied. The results showed that the difference in ignition delays obtained from the flame temperature and O 2 profiles indicated that convection heating was more important than radiant heating for fuel ignition. The transformation of the ignition mode from non-homogeneous to homogeneous with the increase in PAV was confirmed by the changes of flame temperature, residues, and flue gas composition. Flame stability was optimized by the earlier appearance of the continuous flame boundary and was the best at a PAV of 18 m/s. A simplified first-order kinetic model based on the CO 2 evolution profile was established to calculate the reaction rate of the blended fuel during ignition, and the experimental char burnout ratio was consistent with the predicted result. For the potential application of co-firing bituminous coal with a large proportion of semicoke, the recommended PAV may be no more than 22 m/s. • Transition of ignition mode occurred at primary air velocity (PAV) of 22 m/s. • The higher PAV hindered ignition fraction of semicoke in the blended fuel. • The char burnout ratio was well predicted by an Arrhenius expression. • Chemical reaction rate increased due to decreased active energy at high PAV. [ABSTRACT FROM AUTHOR]

High-temperature filtration in coal units is a promising approach for the clean and efficient utilization of coal power. In this paper, a high-temperature precipitator was applied in a 5000 Nm3/h pilot scale platform and especially a full scale 410 t/h pulverized coal boiler, where the precipitator was installed in front of the denitrification unit. The 410 t/h pulverized coal boiler was tested before and after the installation of high-temperature precipitator. The results showed that the particulate matter concentrations at the outlet of the high-temperature precipitator are both less than 8 mg/m3 at nominal 70% and 90% loads. Meanwhile, the outlet concentration increases with the boiler load. The pressure drop for a high-temperature precipitator applying Fe-Al intermetallic membrane is only 500 ± 50 Pa under 90% loads, which is much less than that of conventional fabric filter. Furthermore, gaseous ammonia injection and ammonia escape in the SCR reactor are both decreased under the same denitrification efficiency compared with the typical flue gas pollution post-treatment technologies. The air preheater blockage is potentially the biggest issue for coal-fired power plant and has attracted extensive attention. As expected, the application of the high-temperature precipitator greatly alleviated the negative effects of high fly ash concentrations and reduced the pressure drop for the air preheater during the test. The pressure drops benefit brought by the high-temperature precipitator for the module including high-temperature precipitator, SCR unit, air preheater approaches 1500 ± 50 Pa. Taking a 1000 MWe coal-fired unit and a typical bituminous coal for example, a 1000 MWe coal-fired unit applying the high-temperature precipitator is expected to achieve 30% relevant energy consumption benefit. Furthermore, a total of 4.48 million tons CO 2 emission reduction per year could be achievable if 70% of the Chinese national thermal power market employed them by 2060. • Full scale high temperature filtration (HTP) in the coal-based industry was firstly explored. • The PM concentration at the HTP outlet is <8 mg/m3 at 70% and 90% load. • The HTP pressure drops can be greatly decreased compared to fabric filter. • The HTP application alleviated the negative effects of fly ash for air preheater and SCR. [ABSTRACT FROM AUTHOR]

The effect of the addition of three types of sludge (L, O and F) on both the Na, K and S volatilisation and the slagging behaviour of a bituminous coal (H) was studied. Na, K and S volatilise in the coal, the sludges and their blends partially, and there exist linear relationships between their contents in ashes and the ratio sludge ash/blend ashes for each coal–sludge blend ash series. However, in blends with F (treated with FeCl 3 and lime), S relationship is not linear due mainly to the following effects: a) sulphur retention by CaO to form CaSO 4 , and b) decrease of free CaO due to the formation of ferrites, silicates and phosphates. To determine the slagging tendency, the ash fusion temperatures (AFTs) were related with ash chemical and mineral composition by using the slagging factor, the base/acid ratio, the Fe 2 O 3 /CaO ratio, the P 2 O 5 content, and the ternary equilibrium phase diagram SiO 2 –Al 2 O 3 –CaO. Sludge addition to coal produces a decrease in AFTs that depends on the percentage of sludge added, the sludge phosphorus content and additives (FeCl 3 and/or lime), the fact that ash composition is near to those of the eutectics, and the formation of Si and P amorphous compounds. [ABSTRACT FROM AUTHOR]

The changes in char structure during the fast pyrolysis of three different feedstocks from 600 °C to 1200 °C were investigated. Western Australian Collie sub-bituminous coal, Victorian Loy Yang brown coal and Australian mallee wood were pyrolysed in a wire-mesh reactor at a heating rate of 1000 K s − 1 with holding time ranging from 0 s to 50 s. FT-Raman/IR spectroscopy was used to characterise the structural features of the chars obtained at different temperatures. The combined use of a wire-mesh reactor and an FT-Raman/IR spectrometer has provided significant insights into the rapid changes in the chemical structure of nascent char during fast pyrolysis. Our results indicate that the three fuels began significant ring condensation at different temperatures. Mallee wood showed significant growth of large rings within 1 s holding at 600 °C; however Loy Yang and Collie coals showed significant ring condensation at 800 °C and 900 °C respectively. With increase in temperature to 1000 °C and higher, most ring condensation occurred at < 1 s holding time. The decrease in the intensity of FT-IR spectrum at ~ 1600 cm − 1 confirmed the rapid growth in ring systems at relatively high temperatures. [ABSTRACT FROM AUTHOR]

Raman spectroscopy has been widely used in the structural characterization of various carbonaceous materials. Through spectral deconvolution, FT-Raman spectroscopy has been used to gain insights into the transformation of char structure during gasification, providing new evidence to understand the char gasification mechanisms. These studies have mainly focused on the first-order Raman spectra in the range between 800 and 1800 cm − 1 . Additional information can be gained from the second-order Raman spectra. This study aims to develop a new spectral deconvolution scheme for the second-order Raman spectra of chars from the gasification of coal and biomass. As our initial attempt, the second-order Raman spectra of chars in the range between 2000 and 3300 cm − 1 were deconvoluted into 7 bands representing the main structural features in the chars. Both total Raman peak area and band area ratios are used to gain information about the structural features of char. Using chars from the gasification of WA Collie sub-bituminous coal in CO 2 and H 2 O as examples, the implication of the first-order and second-order Raman spectral data in terms of gasification mechanisms is discussed. [ABSTRACT FROM AUTHOR]

Fast pyrolysis and co-pyrolysis of pine sawdust (SD) and sub-bituminous coal (SB) were carried out in a free fall reactor. There is a gas–solid separator at the bottom of the reactor, where a controlled re-contact of the primary volatiles with the nascent char could be achieved. The experiments of the individual fuels with the volatiles–char re-contact resulted in increased tar yield and decreased the light hydrocarbon gas concentrations compared with that without the volatiles–char re-contact. During the co-pyrolysis of SD and SB, synergies were observed to have produced more tar at different biomass blending ratios (BR). Particularly, the re-contact of the volatiles–char effectively enhanced tar generation and suppressed water formation. The volatiles–char interactions promoted the tar generation mainly at the char bed temperature range from 600 °C to 700 °C. At the optimum condition with the BR of 0.50 and char bed temperature of 700 °C, the tar yield increased up to 28.7%. The co-pyrolysis and volatiles–char interactions favored the acidic components generation in the liquid products. Especially, the volatiles–char re-contact during co-pyrolysis improved the quality of tar by decreasing its asphaltene content. [ABSTRACT FROM AUTHOR]

Ash deposition on the furnace walls and on the tubes reduces the heat transfer efficiency. Hence, it seriously inhibits the stable boiler operation. The ash deposition needs to be removed to restore the heat transfer efficiency to the initial level. The ash deposition experiments for a typical bituminous coal were conducted to understand the mechanisms of growth and shedding of ash deposition. A water-cooled tube was inserted into a furnace, to which fly ash adhered. Based on video camera observations and measurements of the tube surface temperature, a residual layer remained on the tube after shedding of ash deposition was confirmed. A distribution of the particle packing fraction (PPF) of the deposits was calculated, using the pixel percentages of ash particles and pores in the cross-sectional scanning electron microscope (SEM) images obtained. In addition, the particle size distribution and chemical compositions were also analyzed by a computer-controlled SEM (CCSEM). As a result, the initial deposit consisted of a powder layer with a low PPF. Coalescence of the ash particle increased with the growth of the ash deposit. Based on the SEM image of the residual layer remaining after shedding, detachment of the ash deposit occurred in the low-strength powder layer. [ABSTRACT FROM AUTHOR]

Tyre wastes and their blends with coal and a bituminous waste material obtained from the benzol distillation column of the by-product section of a coking plant were employed as a precursor for the production of activated carbons (ACs). Pyrolysis up to 850 °C followed by physical activation with CO 2 yielded mesoporous carbons with different pore size distributions and surface areas depending on the degree of burn-off. ACs with surface areas of 475 and 390 m 2 /g were obtained for the two tyre wastes. The inclusion of coal in the blend gave rise to surface areas of up to 1120 m 2 /g due to an increase in the microporosity. The time needed to obtain the desired degree of burn-off depended on the reactivity of the char. The coal-containing materials required the longest amount of time. The surface chemistry of the samples was studied by Infrared spectroscopy (FTIR) and X-Ray photoelectron spectroscopy (XPS). The principal oxygenated groups found were quinones, lactones and carboxylic acids. [ABSTRACT FROM AUTHOR]