Search

Fine coal reject samples (FCRs) derived from the South African (SA) feed-coal preparation are unsuitable for gasification/combustion. In this novel investigation, two SA FCRs were taken from a thermal-export plant (TEP) and steam-station (STEM) for the coal-property comparison study and pyrolysis/gasification reactivity. H2S/SO2/CO2/Cadmium/Arsenic/volatile organic compounds (VOCs) emissions/dust/particulate-matter pollution linked to pyrite-spontaneous combustion and the interaction of organic sulfur and calcium in FCRs are serious threats to the global human health and atmospheric environment. Numerous investigations primarily focused on SA unoxidized FCR (STEM sample) rather than oxidized FCR (TEP sample) and beneficiated fractions. Furthermore, no Raman/X-ray diffraction (XRD)/density-separation/thermogravimetric results for the TEP (40–400 µm; 83% recovery) and STEM (111–500 µm; 20% recovery) samples have been previously reported. FCRs/their beneficiated fractions were characterized by the different coal analyses. Results indicate that the FCRs have similar properties compared to gasification/combustion feed coals with the exception of higher mineral matter (39% versus 29%), higher vitrinites (43% against 24%) and higher alkali index (8 versus 5) in the TEP sample. Thermogravimetric gasification experiments illustrate higher reaction rates/higher carbon conversion for the TEP sample than the STEM sample. Raman/XRD detected aromatic/aliphatic hydrocarbons/minerals, which positively contribute to the coal's reactivity. Results provide a baseline toward FCRs utilization in pyrolysis/gasification applications on the basis of their reactivity, and a minimization of higher disposal-costs/health-hazards/air-pollution/fines volume. [ABSTRACT FROM AUTHOR]

To evaluate the effect of active alkali and alkaline earth metals (AAEMs) on the co-gasification process, this work studied the gasification/oxidation/combustion reactivity of co-gasification chars acquired at different gasification times by four mixtures: raw coal and raw corn straws (RSM + RCS), acid-washing coal and raw corn straws (HSM + RCS), raw coal and acid-washing corn straws (RSM + HCS), and acid-washing coal and acid-washing corn straws (HSM + HCS). The results indicate that the char contents of the raw/acid-washed samples and mixed samples in the first 5 min of gasification are mainly affected by influence-1 (active AAEMs promote the increase of the char contents during pyrolysis). And after gasification for 10 min, influence-2 (active AAEMs catalyze the reaction of char, resulting in the reduction of char content during gasification) occupies the core position. The order in the effect of active AAEMs on gasification reactivity of char is active AAEMs in RSM and RCS > active AAEMs in RCS > active AAEMs in RSM > no active AAEMs. Among them, the effects of active AAEMs in RCS and active AAEMs in RSM and RCS are very significant. Besides, the ratios of experimental value to theoretical value of residual carbon contents for RSM + RCS chars and HSM + RCS chars range from 19 to 57%, while those for RSM + HCS chars and HSM + HCS chars range from 96 to 103% during oxidation reaction. Active AAEMs in RCS have a significant catalytic effect on oxidation/combustion reactivity of char. The maximum oxidation rate of RCS char is 314 times higher than that of HCS chars. The maximum combustion rate of RCS chars is 15–20 times higher than that of HCS chars. However, the maximum oxidation/combustion rate of RSM chars is less than 2 times that of HSM chars. • Effects of active AAEMs on in-situ pyrolysis-gasification coupling are explored. • The maximum oxidation rate of RCS char is raised by 300 times due to RCS-AAEMs. • The maximum combustion rate of RCS char is raised by 15–20 times due to RCS-AAEMs. • Active AAEMs in RCS can change combustion reactivity of large/small rings in chars. [ABSTRACT FROM AUTHOR]

In this study, the effects of coal blending ratio, pyrolysis temperature, pyrolysis atmosphere and coal particle size on the quality of pyrolyzed char were investigated via a combination of orthogonal experimental design and grey relational analysis. Coal-XG and Coal-LL were pyrolyzed under various conditions to produce chars which were characterized to ascertain their properties such as chemical structure and reactivity. The results indicated that the pyrolysis temperature has the most significant impact on the quality of the char, followed by the pyrolysis atmosphere, coal blending ratio and coal particle size. The increase in pyrolysis temperature not only diminished char yield but also accelerated the consumption of oxygen-containing functional groups and the polycondensation of small aromatic ring structures throughout the reaction process. This led to a reduction in the reactivity of pyrolyzed char and the establishment of a more ordered structure. Meanwhile, the involvement of CO 2 and H 2 O prevented the condensation of small aromatic rings and fostered the generation of additional oxygen-containing functional groups, which resulted in lower yield and higher reactivity of the char under these two atmospheres. Through systematic analysis, only the Raman characteristic parameter I (Gr+VL+Vr) /I D exhibited a strong positive linear correlation with char reactivity, making it a reliable indicator for characterizing the reactivity of char. • The orthogonal design was used to study four response factors. • GRA was used to find optimal conditions and impact ranking of different factors. • Linear regression was applied to relate Raman/FTIR parameters to reactivity. • Blend experiments were conducted with two coking coals. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper investigates the effect of phosphorus (P) on char structure and reactivity of char prepared from the fast pyrolysis of purposely-prepared P-loaded biomass samples at 1000 °C in absence of other inorganic species. Biomass was first acid-washed then loaded with P of three different occurrence forms (one organic P i.e. phytic acid, and two inorganic P i.e. orthophosphoric acid and polyphosphoric acid) at the same P content of 0.8 wt%. Experimental results show that both organic and inorganic P substantially increase char yields during pyrolysis from 6.2% for the biomass sample without P to 23.0–26.0% for P-loaded samples due to the enhanced crosslinking by P-containing structures in char, leading to increases in the char C and H contents and decrease in O content. The presence of P in biochars from fast pyrolysis of various P-loaded biomass samples plays important role in the evolution of char structure and intrinsic reactivity measured during low-temperature oxidation at 500 °C in air under chemical-reaction-controlled regime. After pyrolysis and subsequent char oxidation, all P in biomass either as organic or inorganic P are found to be present in forms of acid-insoluble organic structures. For char prepared from acid-washed wood, char reactivity increases with char conversion due to the increasing pore surface area at higher conversion. Comparatively, for char prepared from acid-washed wood loaded with various P at char conversion below 60%, the presence of P increases char intrinsic reactivity due to the enhanced crosslinking of reactive carbon structures and reduced condensation of char structures. However, at conversions above 60%, P-containing species in char lead to a significant decrease in char reactivity, due to the formation of abundant C O-P bonds, that is highly resistant to the oxidation in air, in the reacting chars. [ABSTRACT FROM AUTHOR]

• High temperature flame combustion study of single wet-torrefied wood particle. • Effects of wet torrefaction (WT) temperature and residence time were studied. • Linear regressions performed to fit ignition, devolatilization and char burnout time. • WT significantly reduces the char yield and TGA-determined char reactivity. • Combustion time increases with WT severity and diminished AAEMs content. In this work, combustion behaviors of single wet-torrefied wood particle in a high temperature flame reactor (1226 °C, 4.2 vol% O 2) simulating suspension biomass fired combustion were studied. 4 mm schima wood spheres were pretreated at various wet torrefaction (WT) conditions (at 175, 200, 225, 250 °C, for 5, 30, 60 min). For the WT pretreated particle has less mass than the raw feedstock, linear regressions were performed to fit ignition, devolatilization and char burnout time with R2 higher than 0.961, 0.995 and 0.988 respectively. The slopes of the fitting lines, indicating the conversion rates, were then used to assess the combustion time on the basis of per sample mass. All three combustion stages, i.e., ignition, devolatilization and char combustion, are prolonged after WT, which is related to the severity of the torrefaction conditions and the diminished AAEMs content. The largest variation lies in the char combustion behavior: the wet-torrefied wood particle produces significantly less char (accumulated char yield reduced from 8.2% to as low as 2.8% after WT), but the char combustion rate decreases up to a factor of 2.4–4.6. The reduced char reactivity is also confirmed by the TGA analysis. [ABSTRACT FROM AUTHOR]

Fuel blending is one of the most effective ways to use biomass to reduce the use of coal. In this study, co-combustion characteristics including NOx emissions, unburned carbon (UBC), and the char reactivity of coal, biomass, and pretreated biomass blends were investigated by using a lap scale drop tube furnace (DTF) and thermogravimetric analyzer (TGA) to evaluate the availability of pretreated biomass from torrefaction or ashless technology to a pulverized coal boiler. In addition, scanning electron microscopy (SEM) was used to analyze the morphology of biomass and pretreated biomass to observe the physical differences between raw samples and their chars. In the results, NOx showed a linear correlation with the content of inherent fuel-N of biomass except in blending cases with ashless biomass. This indicated that the yields of NOx in these cases were higher than both that of single coal and ashless biomass. In addition, UBC declined with increasing the biomass blending ratio for all blending cases, and this can be explained by examining the fuel ratio and SEM images of the fuel samples. Finally, blends with coal and torrefied biomass showed higher char reactivity and lower activation energy than that with ashless biomass as the blending ratio increased. Overall, this paper indicates that it is better to increase the blending ratio of pretreated biomass than raw biomass up to 30% for enhanced reactivity and reduced emissions. [ABSTRACT FROM AUTHOR]

In this work, we study the gasification of pellets produced, after densification, by blending olive mill solid wastes, impregnated or not by olive mill waste water, and pine sawdust under different steam/nitrogen atmospheres. The charcoals necessary for the gasification tests were prepared by pyrolysis using a fixed bed reactor. The gasification technique using steam was chosen in order to produce a hydrogen-enriched syngas. Gasification tests were performed using macro-thermogravimetric equipment. Tests were carried out at different temperatures (750 °C, 800 °C, 820 °C, 850 °C and 900 °C), and at different atmospheres composed by nitrogen and steam at different percentages (10%, 20% and 30%). Results show that the mass variation profiles is similar to the usual lingo-cellulosic gasification process. Moreover, the increase of temperatures or water steam partial pressures affects positively the rate of conversion and the char reactivity by accelerating the gasification process. The increase of the gasification yields demonstrates the promise of using olive mill by-products as alternative biofuels (H 2 enriched syngas). • 4 chars were prepared under slow pyrolysis. • Gasification tests under steam/Nitrogen were performed with pellet/powder states. • Steam molar fraction and temperature influences positively the process. • Impregnation process is advantageous for gasification yields. • Olive mill wastewater is converted from a pollutant to a renewable energy source. [ABSTRACT FROM AUTHOR]

Abstract This work investigates the reactivity of chars produced from Turkish biomass and lignite fuels using a wire mesh reactor at high temperature and high heating rate. The fuels studied were olive residue, almond shell, and Soma lignite. Blends of Soma lignite-olive residue and Soma lignite-almond shell were prepared in proportions of 75:25 and 50:50 wt%, respectively. A wire mesh reactor is used for the pyrolysis of the samples in a controlled inert atmosphere at a uniform temperature of 1600 °C and at a heating rate of above 103 °C s−1. The resulting volatile yields from the wire mesh reactor were compared with those from the proximate analyses. Volatile yield of Soma lignite obtained from wire mesh reactor (53 wt%) was higher than that of the proximate analysis (31 wt%); however, biomasses showed similar yields from both techniques. The morphology and structural changes of the chars were investigated using Scanning Electron Microscopy. Biomass chars displayed a high level of macro-porosity. Combustion reactivity and burnout times of the char samples were determined from thermogravimetric analysis. Biochars had about three times shorter burnout times and three times higher reactivity values compared to those of Soma lignite. First-order kinetic rate constants were determined for all individual chars and blends. Rate constants of the blends showed minor synergistic effect with an increase in the olive residue content, and a pronounced deactivation effect observed with an increase in almond shell content. Highlights • Volatile yields from fast pyrolysis were greater than those from proximate analysis. • Reactivities of the biomass chars were higher when compared to those of the lignite. • Blends with 25% biomass displayed a combustion behavior similar to neat lignite char. • Blends with 50% olive – 50% lignite showed a synergistic effect. • Blends with 50% almond – 50% lignite presented a deactivation effect. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The effect char porosity and metal content have on its reactivity is analyzed. • At 900 °C the porosity is faster developed, attaining high S BET at lower conversion. • Porous structure influenced the reaction rate mainly at early stages. • For X > 0.6 the increase in reactivity is related to the catalytic effect of Ca and K. Abstract A study was carried out on the effect the evolution of the porous structure and metal content have on the gasification rate during char gasification in a conical spouted bed reactor. Partially gasified samples at different temperatures (800–900 °C range) were collected at various conversion levels and characterized by different techniques (N 2 adsorption-desorption, ultimate/proximate analysis and X-ray Fluorescence). At 900 °C there is a fast development of the porous structure, attaining the highest BET specific surface area (S BET) (633 m2 g−1) at low conversion. Char reactivity profiles revealed that the development of the porous structure influenced the reaction rate mainly at early stages, whereas the increase in the gasification rate for conversions higher than 60% (especially at 900 °C) was attributed to the catalytic effect of Ca, K and Fe (the main metals in the ashes). [ABSTRACT FROM AUTHOR]

The present study aims at investigating the effects of porous structure development and ash content on the observed reactivity during steam gasification of biochar residues from a commercial gasifier. The experiments were conducted at a temperature range of 700 to 800 °C using biochar, derived from entrained flow gasification of biomass, under isothermal conditions using a thermogravimetric analyzer. The pore size distribution, surface area and morphology of char samples were determined by N2 physiosorption and scanning electron microscopy (SEM). The results showed that the gasification temperature does not affect the porous structure development considerably. The total surface area of char exhibits a threefold increase, while the total pore volume increase ranges between 2.0 and 5.3 times, at all temperatures. Both properties are directly proportional to the observed reactivity, especially at conversions up to 70%. Catalytic effects of the mineral matter of the char (mainly potassium) become predominant at the later stages of conversion (conversion greater than 70%).

Abstract The firing of biomass or co-firing of biomass with coal has become a common practice in power generation industry worldwide as a cost-effective means to move towards lower carbon footprint. However, the relationship between the properties of biomass and combustion behaviour is not well understood, yet. In this study, we investigated the links between biomass lignocellulosic composition and plant cell wall types, and how they would collectively influence char morphology and reactivity. Five different biomass, i.e. pinewood, distiller dried grains with solubles (DDGS), miscanthus, wheat straw and wheat shorts, in two size fractions were thermochemically pre-treated to alter their lignocellulosic compositions resulting in 50 different samples with varying compositions. Plant cell type and morphology of raw biomass particles were examined using SEM. Biomass char samples were prepared using a fast heating drop tube furnace (DTF) and a slow heating muffle furnace. The morphology of char particles was examined using an oil-immersion microscope whilst the intrinsic reactivity of chars was studied using a thermogravimetric analyser (TGA). Pre-treatments affected most biomass tested in similar trends but to varying degrees, particularly in terms of lignocellulosic composition, cell wall structure and char morphology. Results show that lignocellulosic composition (and plant cell wall types) of biomass correlated well with char morphology and char reactivity. Therefore, it is possible to predict aspects of combustion behaviour from biomass lignocellulosic composition for this selection of samples tested. This work provides a base study for establishing lignocellulosic composition as a key indicator in fuel selection. Highlights • The type of plant cell wall has significant impact on char morphology and reactivity. • The influence of lignocellulose on biomass char morphology is established. • Pre-treatments have profound impacts on lignocellulosic composition and char morphology. • Amount of lignin and cellulose indicates the presence (or absence) of secondary walls. • The combined amount of lignin and cellulose can be used to predict char reactivity. [ABSTRACT FROM AUTHOR]

Summary: The abundant sodium in Zhundong coal can act as an excellent catalyst for its thermal conversion. A horizontal fixed‐bed reactor was selected to minimize the release of Na. Chemical form of Na in the coal was simplified by using acid‐washed coal loaded with H2O‐soluble and NH4Ac‐soluble sodium. Most Na was retained in the char after pyrolysis of the coals at 500°C to 900°C. The H2O‐soluble sodium in Na2SO4‐chars remained unchanged below 700°C and then partly transformed to insoluble sodium; transformation of NH4Ac‐soluble sodium to the H2O‐soluble form dominated in the Na‐chars. SEM‐EDX analysis showed that the Na‐char possessed a smoother surface than the Na2SO4‐char. The Na/C ratio in the Na2SO4‐char increased rapidly with temperature. Raman spectra of the chars showed that loaded Na2SO4 had little effect on its structure, but loaded NH4Ac‐soluble sodium increased the amounts of polyaromatic (≥6) rings and active sites. Reactivity of the char was measured using TGA. Association analysis of these results revealed that insoluble sodium in the char showed excellent catalytic ability, but Na accumulated during oxidation did not. Both the char structure and the amount and occurrence modes of Na had strong effects on the char reactivity. Most Na was retained in the char after coal pyrolysis in the fixed bed reactor at 500‐900 °C. Insoluble sodium in the char showed excellent catalytic ability, but Na accumulated during oxidation did not. Both the char structure and the amount and occurrence modes of Na had strong effects on the char reactivity. [ABSTRACT FROM AUTHOR]

Highlights • Contribution of single coal to the changes of reactivity and structures of chars were studied. • The increase of sub-bituminous coal and decrease of fat coal in blends contribute to the improvement of char reactivity. • Coal blending affects the interaction between coals in blends during coking. • The reactivity of char can be well predicted by the equation: CRI (%) = − 0.029 G R. I + 1.995 V daf − 57.937. Abstract This study investigates the contribution of single coal in blends on the properties of the char produced. Three kinds of coals with varying rank and caking ability were used for the preparation of the chars at 1150 °C in muffle furnace. Char reactivity towards carbon dioxide (CRI) and char strength after reaction (CSR) were tested through the fixed-bed reactor in a laboratory scale and the tumbler, respectively. X-ray diffraction (XRD), scanning electron microscope (SEM), and nitrogen adsorption test were applied to obtain the information for the chemical and physical structures of the char. The study results show that the CRI of char increases with the increase of subbituminous coal content in blends for its role in increasing the surface area and decreasing the crystallite height (Lc) of the chars; the increase of fat coal content in coal blends causes the decrease of the CRI of chars for its contribution to the more ordered crystallite structure and less surface area. The contribution of single coal property in blends to the CSR of chars is just contrary compared to its contribution to the CRI of the chars. Coal blends with high volatile yield and low G R.I value would cause higher surface area and lower crystallite height of char. The CRI of the char can be well predicted by G R.I value and volatile yield of the coal blends quantitatively: CRI (%) = -0.029 G R. I + 1.995 V daf − 57.937 , which is of certain theoretical guiding significance for gasification of char from coal blends. [ABSTRACT FROM AUTHOR]

Blast furnace coal injection is a vital part of modern ironmaking, reducing the amount of coke reductant required in the process and increasing its efficiency. However the injection of different coals or their blends, into the raceway formed by the hot blast, has technical issues due to the very short particle residence times and the limited availability of oxygen in this region. This makes complete burnout difficult and limits the range of coals suitable for this application, leading to partially burnt chars being carried out of the raceway into the blast furnace shaft and potentially into the off-gas system. This paper explores the fate of these chars, from a range of different coals, looking at how this influences the selection for injection and the implication of these on the blast furnace. In particular, we have looked beyond the limitations of selecting coals based on proximate analysis alone by examining in more detail other physical and chemical properties and their potential effect on the process. A drop tube furnace (DTF) has been used to synthesise chars in a high heating rate environment, and although burnout and volatile loss values suggest suitability of some coals for blast furnace injection, additional problematic effects have been identified and measured such as char swelling and agglomeration which may impact the gas permeability of the furnace. A TGA/DSC has been used to measure the gasification of chars by the Boudouard reaction and compare the thermal impact of more reactive samples. While other studies have concentrated on the combustion of injection coals to determine their suitability, this one focuses on the implications of the partially burnt chars formed by incomplete reaction in the raceway. [ABSTRACT FROM AUTHOR]

CO 2 and H 2 O play vital roles in the evolution of char structures and reactivities, particularly in wet oxy-fuel combustion. This work aims to investigate the effects of CO 2 /H 2 O gasification on the characteristics of char prepared in CO 2 /H 2 O/N 2 atmospheres. Lignite samples from Zhundong coalfield in China were pyrolyzed and gasified in different atmospheres at a slow heating rate of 20 °C/min to generate char. Raman spectroscopy was used to identify the microstructure of coal chars, which was correlated with the char combustion reactivity measured with thermogravimetric analyzer in O 2 /H 2 O/CO 2 atmosphere. The combustion reactivity index T index was correlated with Raman structural parameters to demonstrate the applicability of Raman spectroscopy in evaluating char-combustion reactivity. Results indicated that the gasification of CO 2 and H 2 O with coal significantly contributed to the weight loss of char. The Raman band ratio I (Gr+Vl+Vr) / I D decreased and the total Raman peak area increased upon adding CO 2 and H 2 O. Thus, the char became more condensed and contained additional O-containing functional groups. Char-combustion reactivity in oxy-fuel combustion was decreased which originated from the changes in char structures induced by CO 2 and H 2 O gasification. Moreover, T index had positive and negative linear correlations with the Raman parameters I (Gr+Vl+Vr) / I D and I All , respectively. For char prepared in CO 2 -containing atmosphere, the correlation among T index , I (Gr+Vl+Vr) / I D , and I All can be expressed by the function T index  = 13.2299 I (Gr+Vl+Vr) / I D  − 1.7255E-4 I All  + 421.260 with R  = 0.94. [ABSTRACT FROM AUTHOR]

In order to better understand the impact of the carbon structure of char on its combustion reactivity, 14 types of organic model compounds were pyrolyzed under temperatures of 530 °C, 800 °C and 1028 °C at heating rates of 10 °C/min and 65 °C/s, respectively. The carbon structure and the oxidation reactivity of the produced char were determined by respective Raman spectroscopy and thermogravimetric analysis (TGA) methods. The relationships between different reactivity indexes and Raman spectral parameters have been assessed. The results reveal that changes in pyrolysis temperature and heating rate would result in certain evolution of the graphitization degree of char. Good correlations have been discovered between the Raman spectral parameters (A D /A ALL , A GL /A ALL , A (S+R+SL+VR+VL) /A D , and A (GR+VL+VR) /A D) and the combustion characteristic temperatures (T i , T b , T 50 , and T max). From the correlations above, Raman spectral parameter A (GR+VL+VR) /A D is found to be the best correlated to the char combustion characteristic temperature T b with R2 of around 0.76. • Char from 14 types of organic model compounds was studied. • Char yield rises with a higher pyrolysis temperature and a lower heating rate. • Char structure becomes ordered at a high temperature or slow heating rate. • Lower H/C and O/C reflect higher condensation degree of aromatic rings in char. • Higher ordered char structure leads to a higher oxidation temperature. [ABSTRACT FROM AUTHOR]

In this work, single particle combustion of raw and torrefied 4 mm wood particles with different potassium content obtained by KCl impregnation and washing was studied experimentally under a condition of 1225 °C, 3.1% O 2 and 26.1% H 2 O. The ignition time and devolatilization time depended almost linearly on the fuel particle mass. The char conversion time was influenced by both the char mass and char reactivity. Both KCl impregnation and torrefaction promoted char yield, while washing slightly inhibited char formation. The char reactivity was increased by KCl impregnation, decreased by washing, and unchanged by torrefaction. Compared to the raw wood particle, the char conversion time was increased by torrefaction, decreased by washing, and almost unchanged by KCl impregnation due to its promoting effect on both char yield and reactivity. [ABSTRACT FROM AUTHOR]

A critical review and analysis of co-gasification of coal/biomass blends is presented. Initially, the chemistry of gasification of coal and biomass has been described along with different models for pyrolysis of cellulose/biomass. The mechanistic issues of catalytic effect of alkali metals on coal char gasification have been reviewed. This is followed by literature review on gasification of coal/biomass blends in two parts, viz. thermogravimetric and fluidized bed gasification. First part deals with effects of operational parameters on char reactivity. Second part analyzes influence of these parameters on gasification chemistry and producer gas. Factors governing tar content in producer gas have been discussed. Finally, the literature on kinetic modeling of coal/biomass blends has been analyzed. Some new approaches in kinetic modeling of solid-state reactions have been discussed. [ABSTRACT FROM AUTHOR]

This study aims to clarify the effects of inherent inorganic sodium salts present in Zhundong coal on the morphology, element composition, structures, and reactivities of chars from fast pyrolysis. The concentration of the main anions present in the raw coal determined by ion chromatography indicates that Na could exist in the forms of NaCl, Na 2 SO 4 , NaNO 3 , CH 3 COONa (NaAc), and NaHCO 3 , which were then loaded on acid-washed coal respectively by wet impregnation. The pH changes of slurries after the adding of NaAc and Na 2 CO 3 illustrated that sodium carboxylate (–COONa) was generated. The characteristics of chars obtained by fast pyrolysis of the prepared coals in a drop tube furnace were determined. Scanning electron microscopy and energy dispersive X-ray fluorescence spectroscopy of chars revealed that loaded Na, especially –COONa, could be retained on the char surface and inhibit smoothing of the particle surfaces during pyrolysis. Raman intensity indicated that loose char structures formed in chars derived from sodium-loaded coals as a result of inhibiting the process of graphitization and increasing cross-linking density and the number of substitutional groups during fast pyrolysis. Specific reactivities of chars prepared at 900 °C increased in the order: H-char-900 < Na 2 SO 4 -char ∼ NaCl-char < NaNO 3 -char < NaAc-char < Na 2 CO 3 -char, which may be attributed to the combined effects of active Na, active sites, and loose char structures. [ABSTRACT FROM AUTHOR]

The decrepitation of two Chinese lump coals was investigated using high-temperature fast pyrolysis in a purpose-designed furnace to simulate the reaction conditions in the coal-based Corex ironmaking process, and evolution of functional group, porosity, crystallite structure as well as CO2 reactivity of resultant coal chars was characterized. The results demonstrate that the decrepitation index varied significantly for different coal samples and their particle sizes, because of the variable thermal stress induced. The decrepitation index increased with increasing temperature and particle size, and severe decrepitation was observed when coal particles were increased to 20 mm. The coal chars derived from Xinglongzhuang lump coal at different temperatures had much more developed macroporous structure than Datong lump coal chars. A significant change of the crystallite height demonstrated a great influence of temperature on carbon structure. The CO2 reactivity of coal chars decreased with increasing annealing time at different temperatures examined, but the effect of carbonization temperatures on their reactivity has the opposite behavior, which is related to the porosity development and carbon structure variation. The interrelations of these phenomena further suggest that the appropriate dome temperature is crucial for ensuring permeability of coal char bed in Corex except for coal type. Copyright © 2017 Curtin University of Technology and John Wiley & Sons, Ltd. © 2017 Curtin University of Technology and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The pyrolysis of Shengli lignite (SL-Raw) and sodium-based anion doped into coal samples (SL-NaOH, SL-Na 2 CO 3 and SL-NaNO 3 ) was analyzed by investigating the effects of sodium and alkalinity on the differences in crystallite structure of chars by XRD, Raman, XPS and FT-IR. The steam gasification of chars was performed in a fixed-bed reactor. The char gasification results showed that sodium and alkalinity have a catalytic effect on the char reactivity, and the chars have better activity when the sodium compounds are more alkaline. The XRD and Raman results showed that NaNO 3 , Na 2 CO 3 and NaOH inhibited the growth of the aromatic ring structure, and the carbon microcrystalline structure of the chars was destroyed due to sodium atoms during pyrolysis. The XPS and FT-IR results indicated that the phenolic hydroxyl (C OH) was converted into sodium phenolate (C O Na), and the reactivity of chars was better. [ABSTRACT FROM AUTHOR]

Conversion of agro-wastes into energy can be key to a circular-driven economy that could lead to models for sustainable production. Thermochemical processing is an interesting alternative for the upgrading of agro-wastes to energy. However, owing to the complex and largely unknown set of reactions occurring during thermal breakdown, to ensuring consistent quality of the final products is still a goal to achieve at industrial level. The present study investigates the evolution of solid products of pyrolysis, to gain some insights in these complexities. Chars derived from slow pyrolysis (200–650 °C) of citrus pulp in a horizontal reactor have been characterized by means of Fourier Transform Infrared spectroscopy (FT-IR), X-Ray Diffraction (XRD), Thermo Gravimetric Analysis (TGA) and Scanning Electron Microscopy (SEM). Results are discussed also in light of similarities with coal thermal breakdown. At temperatures below 300 °C, changes in solid matrix are mainly due to breaking of aliphatic compounds. Significant changes in char structure and behavior then occur between 300 °C and 500 °C mainly related to secondary char-tar reactions. Above 500 °C, changes appear to occur mainly due to recombination reactions within matrix, which thereby becomes progressively less reactive. [ABSTRACT FROM AUTHOR]

This study investigated effects of blending ratio and alkali and alkaline earth metallic (AAEM) species in the feedstock on char reactivity and producer gas composition in steam co-gasification of chars of blended coal and biomass. Experiments were conducted on a bench-scale fixed bed gasifier in which lignite was used as coal and radiata pine was used as biomass. The blending ratios of lignite to pine (L/P) were, respectively, 0:100 (pure pine), 20:80, 50:50, 80:20 and 100:0 (pure lignite). Lignite and radiata pine were first separately ground to fine particles which were then blended based on pre-set ratios. After this, the blends were pelletized and charred at 900 °C. In order to investigate the effect of AAEM in the coal, experiments were also performed using blended pine and acid-washed lignite from which most of AAEM species were effectively removed. The co-gasification operation temperature was 950 °C. From the experimental results, it was found that the ratios of H 2 /CO, H 2 /CO 2 and CO/CO 2 in the producer gas were nonlinearly related to L/P ratio in the lignite blended chars; however, these gaseous ratios were linearly correlated to the L/P ratio in co-gasification of acid-washed lignite blended chars. In addition, by removing the AAEM species in lignite, yields of H 2 and CO 2 were reduced while CO yield was increased. The char reactivity of acid-washed lignite and pine blends was decreased and this decrease became more significant with increase in coal to biomass blending ratio. [ABSTRACT FROM AUTHOR]

[Display omitted] • High ash coal char reactivity assessment was performed in a packed bed reactor. • High ash coal char reactivity varies with particle size. • The transition of the conversion regime occurred at 1 mm char particle size. • A high H 2 proportion (∼67 %) was obtained by char-steam reaction in a packed bed. • However, H 2 reduces to 45% in oxy-steam char reaction in pilot scale studies. This paper focuses on char gasification in steam towards generating syngas as a part of two-stage gasification technology developed in-house to handle high-ash coal. Controlled experiments in a small-scale packed bed reactor are used to arrive at the dependence of char reactivity using parametric studies like the evolution of temperature, gas composition, flow rate, and carbon conversion rate with time and are compared for different particle sizes. The volume percentages of CO, CO 2 , CH 4, and H 2 were 7, 26, 1, and 66, respectively, in steam char experiments, over a particle size range from 1 mm to 4 mm. If the CO 2 is separated, the H 2 volume percentage reaches 90%. In small-scale experiments, the gas composition for all the particle sizes was invariable; however, the reactivity of small particles is higher than the bigger particles, i.e., 0.5 g/g-hr as against 0.38 g/g-hr for bigger particles due to the transition from diffusion to the kinetic regime, which establishes the suitability of small particles for pilot-scale operations. Finally, the experiments were carried out on pilot-scale char gasification in an oxy-steam environment, and the results were compared with simulated experiments for small-size particles. The consequences of adding oxygen with steam to keep the system auto-thermal are discussed. In the pilot scale under oxy-steam conditions, the volumetric concentrations of CO, CO 2 , CH 4, and H 2 were 10.8, 39.9, 4.7, and 44.6 %, respectively. In contrast, the reactivity increased from 0.46 to 0.90 g/g-hr with a decrease in the calorific value of gas from 9.7 to 8.6 MJ/Nm3. [ABSTRACT FROM AUTHOR]

Pyrolysis, as the initial process of coal clean utilization, is essential to ensure the operation of pyrolysis-gasification decoupling technology. This paper aims to investigate the effects of temperature and oxygen content on coal pyrolysis product distribution and the char structure and reactive properties. Results demonstrate that in the range of 800–1100 °C, the increase in temperature is conducive to the release of volatiles and tar cracking, to enhance the gas phase yield and syngas concentration. However, as Raman spectroscopy analysis shows, higher temperature (>900 ℃) will intensify the graphitization of char, which is not conducive to the next gasification step. In addition, oxygen introduction at 900 ℃ can accelerate the release of volatiles and intensify the occurrence of depolymerization reaction, which increased the gas yields of CO and CO 2 in the gaseous product. Besides, the presence of trace oxygen in the pyrolysis process reduces the degree of coal char graphitization and improves the gasification reactivity. However, at high oxygen content (8 %) conditions, combustion occurs on the surface of the char as SEM results show, which destroys the structure and reduces the gasification activity of the char. Hence, the pyrolysis product distribution and post-pyrolysis char gasification activity can be adjusted by introducing trace oxygen in pyrolysis-gasification decoupling technology. • Fast pyrolysis and gasification decoupling characteristics of Yili coal is studied. • Oxygenated pyrolysis of Yili coal increases gas products yield and reduces tar. • Oxygenated pyrolysis char has lower condensation degree structure. • Coal char from pyrolysis at 900 ℃ is found to have higher gasification activity. [ABSTRACT FROM AUTHOR]

Water inside coal particles could potentially enhance the interior char–steam reactions during pyrolysis and gasification. This study aims to examine the effects of water contents on the char conversion during the pyrolysis and gasification of Shengli lignite. The ex-situ reactivities of chars were further analyzed by a thermo gravimetric analyzer (TGA). Under the pyrolysis condition, the increase in water contents has monotonically decreased the char yields only when the coal particles were small (

• The difference in gasification reactivity of digested solid char with and without AAEMs was systematically clarified. • The inherent AAEMs have promoting effect on gasification reactivity of char. • The E a value of the char after pickling increased 115.76 kJ·mol−1. • The maximum instantaneous CO concentration after char pickling was reduced by a factor of about three. Char reactivity usually determines the overall efficiency of the entire gasification process, while the presence of the alkali and alkaline earth metals (AAEMs) has a catalytic effect on char gasification. In this study, the influence of inherent AAEMs in the gasification behaviour of char was investigated. The char sample was prepared through the pyrolysis of solid digestate derived from anaerobic co-digestion of silage and dairy cattle slurry. The raw char and HCl-washed char were characterized by elemental analyzer, ICP-OES, SEM and XRD to explore their structural changes. HCl-char loses weight in the temperature range of 440–620 °C, and the weight loss percentage is significantly higher than that of char. Ash content of char is reduced by half after a pickling process. AAEMs are largely removed after char acid pickling, resulting in an increase in activation energy of the gasification reaction and a decrease in gasification reactivity, resulting in the gasification reaction time of HCl-char longer than char. Water-soluble AAEM and ion-exchange AAEM affect the evolution of carbon structure, which directly lead to char reactivity during the gasification reaction. As the carbon is consumed, the carbon microcrystalline structure of the residual carbon tends to be ordered, resulting in fewer active free carbon sites for the gasification reaction. Kinetic analysis showed that the loss and deactivation of AAEMs after char acid washing increased the average activation energy E a by 115.76 KJ/mol compared with the original char. [ABSTRACT FROM AUTHOR]

The catalytic hydrogasification of coal char was investigated in a high-pressure fixed-bed tube reactor using CaO, CaCO 3 , Na 2 CO 3 , and K 2 CO 3 as catalysts. Experimental results showed that the char reactivity could be greatly improved with the addition of catalysts. Analysis of char structural evolution was performed to further explore the catalytic mechanism by employing Raman spectroscopy and scanning electron microscopy combined with energy dispersive X-ray spectroscopy (SEM-EDX). The results revealed that CaO catalyst inhibited the aromatic ring condensation of the char structure during hydrogasification. The catalytic reaction of CaO only occurred on the char surface. Na 2 CO 3 or K 2 CO 3 was reduced to metallic Na or K and diffused into the char under hydrogen atmosphere, enhancing the cracking of large aromatic ring systems into small ones, which were the active species for hydrogasification. The catalytic reaction of alkali catalyst occurred simultaneously on the surface of and inside the char. Therefore, the Na 2 CO 3 and K 2 CO 3 displayed higher catalytic activities than CaO in hydrogasification. [ABSTRACT FROM AUTHOR]

CO 2 gasification offers a relatively economical means for coal utilization while minimizing CO 2 emission. Coal ash may play an important catalytic role; however, undesirable ash also causes troublesome problems in the process of CO 2 gasification, especially for that of brown coal featuring high gasification activity and ash content. Therefore, it is necessary to remove the undesirable ash from the brown coal prior to the gasification. Heavy medium separation, one of the most popular ash removing clean technologies, could successfully separate coal fractions with various ash contents according to specific gravity. Consequentially, these coal or char fractions produced from pyrolysis in a newly designed quartz reactor were distinct in certain characteristics, such as ash and maceral compositions, specific surface area as well as carbon structure determined by Raman spectrum in this study, which, in turn, influenced the CO 2 gasification of different char fractions both in the novel fixed-bed quartz reactor and Thermogravimetric Analyzer (TGA). Specifically, experimental results show that the heavier coal/char fractions had less vitrinite and exinite while more inertinite, leading to higher aromatization determinated by Raman spectrum. Carbon structure and content of exchangeable metal ion were the dominant contributors to the different behavior of coal fractions during the isothermal CO 2 gasification, except at high conversion (more than 60 wt.%, daf) of char fractions where ash content played a major role. For the non-isothermal CO 2 gasification in TGA, heavier char fraction presented higher gasification reactivity due to its well-ordered pores. [ABSTRACT FROM AUTHOR]

In order to understand the sensitivity of volatile–char interactions to mild temperatures (600–800 °C), in-situ rice husk char was prepared from fast pyrolysis (>10 3 K s −1 ) on a fixed-bed reactor. Retention of K in char, changes in char structure and char reactivity were determined. The results showed that volatile–char interactions did not cause obvious effect on the char yield but showed an inhibitory effect on char reactivity. The inhibition began only above 650 °C and intensified with temperature rise, but kept almost unchanged at 700–800 °C. Char structure and retention of K have a combined effect on char reactivity. The decreased reactivity was caused by additional volatilization of K from char matrix and transformation of relatively smaller aromatic ring systems to large ring systems (>6 benzene rings) above 650 °C. [ABSTRACT FROM AUTHOR]

CO 2 gasification of torrefied forest residues (birch and spruce branches) was investigated by means of a thermogravimetric analyser operated non-isothermally (400–1273 K) and isothermally (1123 K) under the kinetic regime, followed by kinetic analyses assuming different models. For the non-isothermal gasification, the distributed activation energy model (DAEM) with four or five pseudo-components was assumed. It is found that the severity level of torrefaction had great influences on gasification behaviour as well as devolatilization step. The activation energy of non-isothermal gasification step of three samples varied in the range of 260–290 kJ/mol. The char reactivity decreased with increased torrefaction temperature. For the isothermal gasification, the random pore model (RPM), shrinking core model (SCM), and homogeneous model (HM) were tested. The result has confirmed the trend of decrease in char reactivity with increased torrefaction temperature observed from the non-isothermal gasification. However, different trends in char reactivity due to different wood types were observed by the two methods of gasification. [ABSTRACT FROM AUTHOR]

Although the influence of metallic and alkaline elements on biomass char reactivity is well known, a quantitative assessment of this catalytic effect is hard to obtain because of the chemical and textural complexity of biomass. The effect of K and Si on the CO 2 gasification reactivity of a biomass char was studied using thermogravimetric analysis. A beech sample was pyrolyzed at 800 °C and then impregnated with known amounts of silicon or potassium allowing to obtain a wide range of K/Si ratios. The reactivity of the impregnated samples was studied under a CO 2 (20% vol.) atmosphere. The results show that at low conversion ratios, the char reactivity depends on its textural properties, with strong diffusional limitations. When conversion reaches 60%, the presence of a catalyst (K) and an inhibitor (Si) becomes the major parameter influencing reactivity. From these experiments, a general trend was obtained between K/Si ratio and reactivity as a function of conversion. [ABSTRACT FROM AUTHOR]

The catalytic properties of raw biomass chars and Ni-loaded biomass chars prepared at a high-heating-rate were assessed in the methane decomposition reaction. The raw chars exhibited a moderated catalytic activity in methane cracking while the Ni-loaded chars showed a catalytic activity 10 times higher than the raw chars. The deposited carbon was a highly ordered one as evidenced by XRD, Raman analysis and oxygen reactivity tests. The activation energy in the combustion reaction was estimated to be 300 kJ/mol. These results indicate that biomass char can be an effective low-cost and active support for metal impregnation to be used in catalytic cracking of hydrocarbons for hydrogen production. [ABSTRACT FROM AUTHOR]

In this study, a theoretical model of biomass char gasification reactivity was developed, focusing on the catalytic effect of inorganic elements on the char gasification process. A comparison with previous research results shows that the catalytic ability of K in a fixed bed reactor is stronger than that of Ca, while the catalytic ability of Ca in a fluidised bed reactor is stronger than that of K. The migration and transformation of K and Ca in a fixed bed reactor and fluidised bed reactor are compared. In the fluidised bed reactor, a larger proportion of Ca is transformed into an ion-exchanged state than K, which is contrary to the experimental results in the fixed bed reactor. Then, according to the equivalent-volumetric impregnation method, the saturated loading ratio of K was determined to be 35%, and the full catalytic ratio of K was determined experimentally. Finally, eight typical biomass char samples were selected to perform experiments at different temperatures in the micro fluidised bed reactor to determine the char gasification reactivity, and the results were compared with the calculated values of the model. Results show that the model can effectively predict the char gasification reactivity both in trend and accuracy. [Display omitted] • Migration and transformation of K and Ca during pyrolysis process were clarified. • The catalytic ability of inorganic elements in fluidised bed reactor was quantified. • The order of catalytic ability in the fluidised bed reactor is Ca > K > Na > Fe > Mg. • The model considers catalytic/inhibitory effects of seven main inorganic elements. • The self-developed char reactivity model is suitable for the fluidised bed reactor. [ABSTRACT FROM AUTHOR]

In the present study, the hydrogasification of chars produced from different rank coals was carried out in temperature up to 1123 K and in the pressure of 5 MPa using a high pressure fixed bed reactor. The experimental results show that the char hydrogasification process can be divided into two stages: an initial stage with sharp decline in hydrogasification rate and a stable stage with slower decline one. To further explore the hydrogasification mechanism, Raman spectroscopy was used to investigate the evolution of the char structure during hydrogasification. The initial stage can be attributed to the rapid reaction of hydrogen and the functional groups, amorphous carbon remaining in char. The stable stage owes to the gradual consumption of amorphous carbon and the ordering of the microstructure, which was indicated by the decrease in I D3 / I G and the increase in I G / I ALL with the increasing carbon conversion. Good linear correlations were found between the hydrogasification reactivity and the band area ratios of ( I D3 + I D4 )/ I G and I D1 / I G , which denote the active sites and the degree of graphitization of chars, respectively. [ABSTRACT FROM AUTHOR]

Slow pyrolysis (200–650 °C) experiments on citrus residues (orange peel waste “OP” and lemon peel waste “LP”) were carried out in lab scale fixed bed batch reactor. Bio-oil and bio-char obtained by thermal degradation are more stable, more homogeneous and higher energy content fuels when compared to the parent feedstock. Thermogravimetric analysis (TGA) showed higher stability of LP waste, which appears related to the higher lignin content . Mass and energy yields of solid and liquid products (i.e., char and oil) were measured to determine the effects of peak temperature on feedstock. A linear correlation between Gross Calorific Value (GCV), peak temperatures and mass loss (ML) allows easy analytical calculation of energy properties of residues in the range between 200 °C and 325 °C (peak temperatures). Highest GCV and energy density (ED) of bio-chars are obtained at 500 °C peak temperature for both LP and OP residues: ED LP_CHAR = 1.70, ED OP_CHAR = 1.75. Char reactivities were measured in TGA in a nitrogen atmosphere. High temperature chars (500 and 600 °C) showed a higher reactivity than low temperature ones, between 100 °C and 400 °C. This higher reactivity may be explained by the higher thermal conductivity due to higher ash content and higher surface area of high temperature chars. The tars extracted from pyrolytic bio-oil showed GCVs of approximately 19,700 and 17,000 J/g for LP and OP, respectively, independently of pyrolysis peak temperature. Despite the difference in the GCVs, both LP and OP tars show nearly identical FT-IR spectra denoting the presence of very similar chemical species, mainly phenolic, polyaromatics, ketones, ethers and carboxylic acids. [ABSTRACT FROM AUTHOR]

Gasification is one route to produce chemicals and liquid fuels from biomass. The gasification of the char is catalyzed by alkali and alkaline earth metals in the biomass. In this work the catalytic effect of calcium (Ca) and potassium (K) on CO 2 gasification of spruce wood was studied using a thermo gravimetric analyzer (TGA). The ash-forming elements were first removed from the wood using an acid leaching method. Then, various concentrations of K and Ca were absorbed to the wood by ion-exchange to carboxylic and phenolic groups, impregnation of K 2 CO 3 or physically mixing of CaC 2 O 4 . The prepared spruce samples were placed in a mesh holder and gasified in the TGA at 850 °C in 100% CO 2 . The results demonstrate that the gasification rate of the char increased linearly with an increase in the concentration of Ca or K. Crystalline CaC 2 O 4 distributed only at the surface of the wood particles resulted in low catalytic activity. The catalytic activity of Ca was higher than K in the beginning of char gasification but the catalytic effect of Ca decreased earlier than the catalytic effect of potassium. Further, the char structure was investigated by SEM–EDX. The SEM analysis from interrupted gasification experiments showed the formation of CaCO 3 and K 2 CO 3 layer on the char surface. By adding corresponding levels of Ca and K as the original spruce to the acid washed sample, a similar gasification reactivity was obtained at 850 °C. [ABSTRACT FROM AUTHOR]

The thermal pyrolysis of two lump coals used in the Corex process was carried out, and the structure, strength and reactivity to CO 2 of the resulting chars were comprehensively investigated. The results show that the characteristic of the resulting chars is greatly affected by coal properties and carbonization conditions. XLC char forms visible pores because of its good thermoplastic property, and the bigger pores could affect the yields of volatiles. However, fissures are produced in DLC char during pyrolysis due to the non-caking property and cracks appear to decrease the production of pores. With the increasing annealing time and temperature, pore size and pore volume of chars decrease, which can be related to the shrinkage of coal char. The mechanical strength of chars is enhanced with increasing carbonization time and temperature, but the crushing strength of DLC chars is significantly influenced by cracks. Chars produced with longer time and higher temperature primarily display a lower CO 2 reactivity according to the gasification tests. The results further indicate that factors affecting the CO 2 reactivity are different for the two series of chars. The char reactivity index appears to have a linear correlation with the char strength after reaction. [ABSTRACT FROM AUTHOR]

The hydrogasification reactivity of charN 2 and charH 2 , obtained from Sulcis coal pyrolysis at 900 °C in inert and reductive atmospheres, respectively, was investigated in a commercial microreactor under temperature programmed reaction (TPR) at high-temperature (700–800 °C) and high-pressure H 2 (1.0–5.0 MPa) conditions. The flue gases were analyzed online by FTIR spectrometry for the identification of volatile species produced. The emissions of carbon (CO 2 and CO) coming from both chars reached the maximum releasing rate below 500 °C, whereas nitrogen-based compounds (HCNO and NH 3 ) were solely detected during the hydrogasification reaction of charN 2 . Meanwhile, the main product of char hydrogasification CH 4 was detected at temperature as low as 450 °C. Generally, the carbon conversion values of charN 2 were higher than those of charH 2 . At low-temperature and pressure reaction conditions the carbon conversion of charH 2 rapidly went down. A first-order reaction rate dependence on H 2 pressure at 800 °C was found for charN 2 , whereas the reaction order was almost double for charH 2 . The apparent activation energies of charN 2 –H 2 reaction at 1.0 and 5.0 MPa pressures were 96 and 78 kJ mol − 1 , respectively, whereas the apparent activation energy for charH 2 –H 2 reaction under 5.0 MPa pressure was 140 kJ mol − 1 . The Sulcis coal reactivity during the hydrogasification process was significantly impacted by the pyrolysis conditions used in getting chars. [ABSTRACT FROM AUTHOR]

Benzene removal using spruce wood char as catalyst was investigated. The influence of pyrolysis temperature and activation with CO2 on the char structure and reactivity for benzene adsorption and cracking was analyzed. The structural features of the char were examined by the CO2 adsorption technique and Fourier transform infrared spectroscopy (FTIR). The reactivity for benzene removal was investigated using a fixed bed quartz reactor. Surface analysis showed that the microporous char surface area was influenced by the pyrolysis temperature and was almost doubled by activation with CO2. The benzene adsorption capacity of the char decreased with increasing pyrolysis temperature. Activation with CO2 however, increased the fraction of adsorbed benzene by a factor of two and 10 for char produced at 500 and 800 °C, respectively. The total microporous surface above 700 m²/g was found to be a good indicator for the reactive char surface for benzene cracking at high temperatures. At 1050 °C the main mode of benzene conversion was homogeneous thermal decomposition. We confirmed that wood char has the potential to serve as an effective catalyst for benzene removal. However, benzene decomposed over the charcoal by carbon deposition which led to a fast deactivation of the wood char catalyst. [ABSTRACT FROM AUTHOR]

Highlights: [•] Pyrolysis of oil refinery sludge has been studied in a pilot plant reactor. [•] Temperatures in the range 350–530°C were used in a nitrogen atmosphere. [•] Gas, liquid and char fractions were characterized. [•] An increase of liquid fraction is observed when increasing the temperature. [•] Light hydrocarbon yields increase with temperature. [ABSTRACT FROM AUTHOR]

Highlights: [•] X-ray CT was used to visualize the anisotropic internal structure of wood cylinder char. [•] Heating rate during pyrolysis influenced the radial shrinking and swelling of wood cylinder. [•] Heating rate during pyrolysis also influenced the pore size and shape. [•] Pore diffusion played an important role in the gasification of large wood-derived char. [•] The evolution of particle shape during gasification was anisotropic in the diffusion-controlled region. [Copyright &y& Elsevier]

Abstract: The influence of initial water content and temperature on the pyrolysis product distribution as well as on the structure and reactivity of the pyrolysis char was investigated. Spruce wood chips with 2.4%, 16.4%, and 55.4% initial water content were pyrolyzed in a tubular batch reactor at 500 and 800°C with a heating rate between 4 and 12.6°C/min. The structural features of the char samples were examined with scanning electron microscopy, Brunauer–Emmett–Teller (BET) method, and mercury porosimetry. The reactivity in CO2 was investigated using thermo-gravimetric analysis and a fixed bed quartz reactor. It could be seen that higher water content led to a higher yield of condensable products and a lower amount of char. At a pyrolysis temperature of 500°C the CO-content of the product gas did increase significantly with increasing water content. Moreover, initial water content had no significant effect on the microscopic structure of wood chars. The specific char surface area did increase with increasing initial water content up to the fiber saturation point. It was also observed that the specific char surface area was strongly influenced by the pyrolysis temperature. When the pyrolysis temperature increased from 500 to 800°C, the BET surface area became at least 200 times smaller and the average size of micropores became about 10 times smaller. Most likely, pyrolysis at 800°C induced more secondary reactions that were responsible for the occlusion of the micropores within the char [1]. Finally, it was found that reactivity in CO2 significantly decreased with increasing pyrolysis temperature. However, initial wood water content did not have a significant effect on char reactivity in CO2. [Copyright &y& Elsevier]

Abstract: Steam plays a vital role in the gasification process. This study aims to investigate the changes in char structure and reactivity during the gasification of Victorian brown coal. A Loy Yang brown coal sample was gasified at 800°C in a novel fluidised-bed/fixed-bed reactor in three different gasification atmospheres: 15% H2O balanced with argon, 4000ppm O2 balanced with CO2 and 4000ppm O2 +15% H2O balanced with CO2. The intrinsic reactivities of chars with air were measured with a thermogravimetric analyser (TGA) at low temperatures (380 or 400°C). The char structural features were characterised using FT-Raman spectroscopy followed by spectral deconvolution. Our results indicate that steam, when it is present in the gasifying atmosphere, has a drastic effect on char structure and the subsequent reactivity of char with air at low temperatures. The presence of steam during the gasification at 800°C also impacts on the volatilisation of Mg and Ca by altering the char structure. Our data provide evidence that the char–H2O gasification follows a different reaction pathway from the char–CO2 gasification, at least for the gasification of Victorian brown coal under the current experimental conditions. [Copyright &y& Elsevier]