Charcoal Research Articles

Entrained-flow pyrolysis and (co-)gasification characteristics of Indian high-ash coals

Co-utilization in entrained-flow gasifiers is a potential solution to address the high ash-related problems persistent in fluidized-bed gasifiers. This work presents the hitherto unreported high-temperature (1000–1400 °C) entrained-flow pyrolysis and (co-) gasification characteristics of Indian high-ash coals and two candidate fuels (indigenous bituminous coal and petcoke) for possible co-utilization. Char analyses – TGA, FTIR, Raman, and SEM − are also performed to characterize the pyrolysis-induced structural changes. Volatile yields of candidate fuels matched with proximate values while those of high-ash coal exceeded by ∼12 wt%. Thermal deactivation was more pronounced for coal chars. High-ash coals achieved 100% carbon conversion at conditions exceeding 1300 °C and 20 vol% CO2. Bituminous coal showed comparable conversions, 70−90%, at identical conditions; further increase in conversion potential may be possible through steam addition due to enhanced char deactivation and pore diffusion effects at higher temperatures. Petcoke achieved lowest conversion of ∼30% even at the severest conditions; decreasing the average particle size by half showed an improvement of only ∼15%. Co-gasification of high-ash coal and petcoke blends showed no synergy. Considering closely matching carbon conversion, volatile release potential, and industry-standard slag tapping temperatures (1300−1500 °C), indigenous bituminous coals are more promising for co-utilization with high-ash coals in autothermal entrained-flow gasifiers.

Graphitization: Microstructural and microtextural transformations of residual char from international coal combustion ash

Natural graphite is a critical raw material and its substitution in some applications will contribute to reduce its supply risk. Coal ash, which is still produced in high amounts, contains a carbonaceous solid residue (char) that may be a substitute of natural graphite. For this purpose, char may be graphitized and used in electrocatalysis reactions, however char properties depend on coal rank, composition and combustion conditions that affect the graphitization process. Research on industrial coal char graphitization is limited, resulting in restricted comprehension of the contributing factors. In order to provide novel insights, industrial residual chars (derived from Poland, Portugal, Romania and South Africa) subjected to high-temperature treatments (carbonization at 1000 °C followed by treatment at 2600 °C under environmental pressure) were examined regarding their microstructural and microtextural transformations. The samples were studied by focussing on its heterogeneity, namely its specific properties and interactions, including elemental composition, optical character, and structure. Furthermore, the evolution of structural order of selected char morphotypes in samples derived from coal of similar rank was assessed using Raman microspectroscopy.The results highlighted a set of aspects that could have influenced the transformations experienced by the different chars during high temperature treatments (graphitization). It was found that Hydrogen might play a role in the graphitization ability of isotropic chars derived from low rank coal. The prior preferential orientation of the Basic Structural Units (BSU) contributes to achieve a higher graphitization degree, but it can be enhanced or hindered by other factors, e.g., hydrogen content. Raman microspectroscopy showed that char morphotypes from the same group underwent different transformations during graphitization, indicating that morphotypes or sections with unfused optical character may be more prone to graphitization. However, the existence of disordered domains and specific microtextures, such as polyhedral pores identified under TEM, likely hindered further graphitization. Further research on this topic is needed.

An investigation to enhance the performance of molten carbonate-direct coal/carbon fuel cells through improvements in anode layouts and the compositions of carbonate electrolyte

Two anode configurations are systematically tested in composite electrolytes of molten carbonate with Cs2CO3 at various temperatures using different carbon fuels, including bituminous coal, bituminous coal char, carbon black, and graphite powder. The results of electrochemical impedance spectroscopy show that electrolytes composed of (Li-K)2CO3 62:38 doped with 20 wt% Cs2CO3 and utilizing graphite powder as a fuel exhibit reduced ohmic and charge transfer resistance. This can be attributed to the decreased surface tension, which enhances the gas solubility of the reactants within the electrolytic matrix. The analysis of particle size distribution through laser diffraction reveals that the graphite specimen has the smallest mean particle size, resulting in an enhanced rate of electrochemical oxidation. The ultimate and proximate analysis indicates that graphite powder has a lower moisture and ash ratio along with a significantly higher fixed carbon content compared to other carbon fuels. Therefore, the obtained V-j &P-j curves in Anode 1 illustrate that graphite powder yields the highest current density and power density of 903 mA/cm2 and 172 mW/cm2, respectively, at an operating temperature of 680 °C under the laboratory conditions. These values surpass those reported in the existing literature. In contrast, Anode 2 exhibits low performance, due to ash particles regime-controlled at the lower part of the chamber during the coal pyrolysis. Based on results, we suggest that graphite powder is the promising fuel candidate for MC-DCFC to achieve the higher performance.

Varied impacts of volatiles from pyrolysis of poplar wood, bark and leaves on property of coal char

Co-pyrolysis of coal and biomass could tackle undesirable properties associated with coal-tar or bio-oil, while cross-interactions between volatiles and chars of varied origin are very complex but important in shaping property of pyrolytic product. Herein, the volatiles from pyrolysis of poplar wood, bark or leaves were forced to pass through coal-char in lower bed at 600 ºC, aiming to investigate specific interactions of the volatiles with the coal-char. The results indicated that the biomass-derived volatiles did interact with the coal-char and formed additional carbonaceous deposit via mainly cracking reactions, increasing yield of coal-char (i.e. 7.1 % increase with wood-derived volatiles while 19.6 % increase with leaves-derived volatiles). Cracking of volatiles from poplar wood or bark on coal-char formed very aromatic carbonaceous deposit, enhancing overall carbon content while causing coarse surface of the coal-char. The leaves-derived deposit was more oxygen-rich, which, however, still enhanced thermal stability and crystallinity of graphitic carbon crystals in the modified coal-char. Additionally, the coal-char modified with the biomass-volatiles became more hydrophobic, despite the increased abundance of the oxygen-containing species like CO and C–O–C. The modification of elemental composition and aromaticity of coal-char through interaction with the biomass-derived volatiles resulted in higher capability for adsorption of phenol.

Investigation on the correlation between AAEMs transformation and reactivity synergy during the co-combustion of biochar and coal char

Co-combustion synergy behavior was caused by the coupling effect of AAEMs in different chemical forms but co-combustion synergy mechanism was currently unclear. In the study, co-combustion reactivity and synergy behavior of blends of rice straw char (R) and coal char (C) and blends of pretreated R (washed by NH4Ac solution) and pretreated C were investigated. AAEMs transformation during co-combustion was analyzed based on experimental and simulation methods and co-combustion synergy mechanism was proposed. The results show that as temperature increased from 500 to 800 °C, synergistic effect firstly decreased and then increased with an extreme point at 600 °C. For pretreated blends, transformation of HCl-soluble K in R to H2O-soluble K could catalyze the residual semi-char reaction, leading to synergistic effect. KCl in R has higher catalytic and migration activity compared to active Na/Ca in C, therefore synergistic effect was generally improved when KCl was present in blends. Thermodynamic simulation demonstrated that KCl volatilized significantly at temperature ranging from 700 to 800 °C. Therefore, synergistic effect increased with temperature increasing from 600 to 800 °C. Formation of stable Na–Ca–Si combeite reduced SiO2 transformation into liquid and covering C surface, and thus cause an increased synergistic effect at 700–800 °C.

An Assessment of Plant Growth and Soil Properties Using Coal Char and Biochar as a Soil Amendment

Soil degradation due to loss of soil organic carbon is a serious concern in semiarid agroecosystems. Biochar and other organic char products have long been known to increase soil organic carbon. In this study, three-year field observations were carried out on use of coal char (CC) and biochar (BC) as soil amendments in unirrigated semiarid rangeland soil. Coal was pyrolyzed at three different temperatures of 650, 750, and 800 °C to form CC650, CC750, and CC800, respectively, and BC was obtained from a local commercial producer. Manure, CC, and BC were incorporated in soil at 10% (v/v). Analyses of plant growth (aboveground biomass) and soil properties were performed and compared with the control treatment without char. In all three years, CC applied with manure (CC650M) produced significantly greater grass biomass, by 95, 42, 101%, and BC applied with manure (BCM) increased grass biomass by 89, 39, 52% in 2018, 2019, and 2020, than the controls in the respective years. Soil tests a year after application of char indicated significantly increased soil organic matter (OM) with CC and BC treatments (1.60–2.93%) compared with the control (1.37%). However, further detailed studies are required to investigate CC and BC interactions with soil in unirrigated semiarid rangelands.

The Diversity in Tobacco Use Among Women of Reproductive Age (15-49 Years) in Pakistan: A Secondary Analysis of a Multiple Indicator Cluster Survey 2016-2018.

Tobacco use in women of reproductive age group (15-9 years) may contribute to poor maternal and child health outcomes. We estimated the prevalence of smokeless tobacco (ST), cigarette, and waterpipe use among these women in Pakistan and explored associations with socio-economic differences and birth weights after recent childbirths (past 2 years). We used the Multiple Indicator Cluster Surveys datasets from three provinces in Pakistan. Prevalence was generated for current use of tobacco among women with recent childbirth (WWRC) and without recent childbirth (WWoRC). We further compared socio-economic status and birth weights between tobacco users and non-users. The prevalence of current ST use was 1.4% and 2.5%, and waterpipe smoking was 1.2% and 1.8%, in WWRC and WWoRC, respectively. ST use varied across Pakistan's provinces by 13 percentage points in WWRC and WWoRC while waterpipe smoking by 10 and 15 percentage points, respectively. The odds of using any form of tobacco were significantly lower with higher levels of education or wealth index. Compared to children born to mothers who did not use tobacco, the birth weight of children born to mothers who smoked waterpipe was on average 0.83 kg (95% CI -1.6 to -0.1) lower whereas it was 0.33 kg (95% CI -0.9 to 0.3) higher for ST users. Tobacco use among women of reproductive age in Pakistan varied significantly based on province and tobacco type. Waterpipe smoking was associated with a reduction in birth weight. Raising awareness of the harms of tobacco use among women of reproductive age and targeting interventions in high-burden regions of Pakistan should be prioritized. The prevalence of current smokeless tobacco use and waterpipe smoking varied significantly in Pakistan (~13 and ~15 percentage points, respectively) among women of reproductive age, and there seems to be little change in tobacco use behavior around pregnancy and early motherhood. The study highlights a need to better understand the prevalence of tobacco use in Pakistan, and further contextual research is warranted to understand the reasons for such high tobacco use in certain areas. This information highlights the need for improving current tobacco control interventions and policies, including measures that could help reduce its use and prevent its uptake. Furthermore, compared to children born to mothers who did not use any form of tobacco, we found a statistically significant difference (830 g) in birth weight for babies born to mothers who at the time of the interview smoked waterpipe and a non-statistically significant difference of about 330 g for children born to mothers who at the time of the interview used smokeless tobacco. In addition to our findings, some literature suggests the association of waterpipe smoking with low birth weight. A possible explanation could be the exposure to smoke that contains toxicants from the tobacco product itself in addition to the burning of charcoal, which is required when using waterpipe. Waterpipe smoking also results in high exposures to carbon monoxide and polycyclic aromatic hydrocarbons, which are known to be carcinogenic and teratogenic. In terms of smokeless tobacco use, further research is warranted to understand its impact on birth outcomes through longitudinal studies accounting for diverse products, its constituents and the amount of consumption.

Development of a three-stage process for high coal desulfurization and char yield

Efficient pyrolytic desulfurization with high char yield is a promising yet challenging approach for the cleaner utilization of abundant high-sulfur coal reserves. In this study, we have discovered that a single pyrolysis process under either oxidizing or reducing conditions cannot efficiently remove various sulfur forms while preserving a high char yield. To address this challenge, we propose a three-stage desulfurization process: a low-temperature oxidative pyrolysis (LTOP), a high-temperature reductive pyrolysis (HTRP), and a dry magnetic separation process. LTOP operates in a fluidized bed for only a few minutes to oxidize the diamagnetic pyrite particle surface to Fe2O3 while minimizing char losses. HTRP occurs in another fluidized bed for an appropriate duration to substantially remove organic sulfur while reducing Fe2O3 to highly magnetic Fe3O4 or Fe. Partially magnetized pyrite particles are then removed from the char through magnetic separation. When applied to anthracite coal with a total sulfur content of 4.99%, this process achieves nearly 100% desulfurization for pyritic sulfur and 74.81% for organic sulfur. Ultimately, it recovers 94.5% of the original coal excluding volatiles as char, with 91.6% being low-sulfur char.

Novel application of sustainable coal-derived char in cement soil stabilization

Cement soil stabilization is a commonly used method to improve in-situ soil properties catering to different geotechnical applications. However, cement manufacturing is typically associated with high CO2 emissions and energy consumption. Coal char is a sustainable and environmentally friendly material derived from the coal pyrolysis process. Traditionally used for combustion and gasification, recent research has revealed its potential to improve the engineering performance of cement-based construction and building materials. This study explores the innovative use of coal char in cement soil stabilization. Examining various cement contents (5%, 10%, and 20%) and char contents (10%, 20%, and 30%), the properties of char-cement stabilized soils, including mineralogy, density, water content, thermal conductivity, unconfined compressive strength (UCS), and mechanical properties under triaxial compression, are comprehensively investigated and compared with cement stabilized soil. It is found that char promotes both cement hydration and reaction between soil minerals and cement. The thermal conductivity and UCS of char-cement stabilized soil are 0–9% lower and 8–16% higher, respectively than that of cement stabilized soil. Under triaxial compression, the addition of char in stabilized soil leads to 23.7% increase in shear strength, 17.7% increase in cohesion, and 16.7% increase in the angle of internal friction. In conclusion, the introduction of coal char into traditional cement soil stabilization demonstrates a novel approach to achieving sustainability and enhancing engineering performance in relevant geotechnical applications.

Mobility, Seasonal Encampments, and Temporary Dwellings of Charcoal Burners: New Insights from an Ethnoarchaeological Study in Morocco

ABSTRACT Pre-industrial economic activities related to the seasonal exploitation of forest resources, including charcoal production, are associated with temporary settlements and mobility in European and Mediterranean outlands. Because they have left few, ephemeral traces in the archaeological record, these temporary dwellings and the itinerant lifestyles associated with them are largely unknown. To better detect and interpret such remains, we conducted an ethnoarchaeological study in Morocco, where some charcoal burners still maintain an itinerant lifestyle. We first examine the types of seasonal temporary encampments of contemporary charcoal burners in two regional contrasting regions, Gharb and Middle Atlas. We then address three archaeological issues: 1) the individual variation and the skills and dispositions of charcoal burners in adapting the architecture and organization of their encampments, 2) the impact of natural and anthropogenic post-depositional processes on site formation, and 3) the difficulty of associating a temporary dwelling with a particular economic activity.

New insights into the heterogeneous reduction of NO on coal char based on molecular configuration evolution

No report reveals the relationship between coal char molecular configuration and NO heterogeneous reduction. Here, the molecular configuration of char, including pore structure and microcrystalline morphology, was well characterized through synchrotron radiation-based SAXS and WAXS. Furthermore, the universal relationship between molecular configuration and NO heterogeneous reduction was revealed. The adsorption configurations of NO on different defects were calculated through density functional theory (DFT). The results indicate that smaller pores are affected by both monolayer structure and layer stack characteristics, while larger pores are primarily dominated by the latter. The NO decline rate and final reduction efficiency of large higher-rank chars are driven by NO diffusion in larger pores. On the other hand, the active sites and flow patterns in smaller pores synergistically control the decline rate and reduction efficiency of small higher-rank chars. As for lower-rank chars, the diffusion in larger pores and the flow patterns in smaller pores affect the reduction efficiency and decreasing rate of NO, respectively. It is important to note that edge defects control the initial stage of NO reduction, while the single-vacancy and double-vacancy defects dominate the heterogeneous process in the final NO reduction stage. The findings can provide theoretical support for better predicting the NO heterogeneous behavior and thus promote the development of novel ultra-low NOx combustion technologies.

An improved semi-global intrinsic kinetics model for high temperature carbon oxidation

Measurements of the oxidation rates of various forms of carbon (soot, graphite, coal char) have often shown an unexplained attenuation with increasing temperatures in the vicinity of 2000 K, even when accounting for diffusional transport limitations and gas-phase chemical effects (e.g. CO2 dissociation). With the development of oxy-fuel combustion approaches for pulverized coal utilization with carbon capture, high particle temperatures are readily achieved in sufficiently oxygen-enriched environments. In this work, a new semi-global intrinsic kinetics model for high temperature carbon oxidation is created by starting with a previously developed 5-step mechanism that was shown to reproduce all major known trends in carbon oxidation, except for its high temperature kinetic falloff, and incorporating a recently discovered surface oxide decomposition step. The predictions of this new model are benchmarked by deploying the kinetic model in a steady-state reacting particle code (SKIPPY) and comparing the simulated results against a carefully measured set of pulverized coal char combustion temperature measurements over a wide range of oxygen concentrations in N2 and CO2 environments. The results show that the inclusion of the spontaneous surface oxide decomposition reaction step significantly improves predictions at high particle temperatures. Furthermore, the simulations reveal that O atoms released from the oxide decomposition step enhance the radical pool in the near-surface region and within the particle interior itself. Incorporation of literature rates for O and OH reactions with the carbon surface results in a reduction in the predicted radical pool concentrations and a very minor enhancement of the overall carbon oxidation rate.

Effect of ammonia on N migration and transformation characteristics during coal pyrolysis: Quantum chemical calculations and pyrolysis experiments

The co-firing of the non-carbon fuel, ammonia, with pulverized coal, is an effective way to reduce CO2 emissions in thermal power plants. However, the high nitrogen content of ammonia increases the risk of high NOx emissions during the co-firing process. To achieve low nitrogen combustion of ammonia-coal co-firing, it is necessary to study the impact of ammonia on the N migration and transformation characteristics, during the coal pyrolysis and combustion processes. In this work, the effects of ammonia on the release of N-containing products, during coal pyrolysis, were studied by quantum chemistry calculations and pyrolysis experiments. The theoretical calculation results showed that the mixing of hydrogen-rich ammonia fuel promoted the generation of HCN during coal pyrolysis and increased the energy consumption of HCN generation. Additionally, ammonia-N could be embedded into the coal char structure and exist in the form of N-6. The experimental results indicated that with the temperature increasing, the N content of the coal char and the pyridinic-N increased under the condition of ammonia-coal co-pyrolysis, confirming the microscopic mechanism of ammonia-N embedding into the coal char structure, as indicated by the theoretical calculations. Our work reveals the molecular paths of N migration and transformation and elaborates on the interaction mechanism of ammonia-N and coal-N during the ammonia-coal co-pyrolysis, which has a certain promoting effect on the development of ammonia-coal co-firing mechanism.

CARBON MONOXIDE POISONING: LITERATURE REVIEW

Carbon monoxide (CO) is known as a colorless, odorless, tasteless, and non irritating gas. CO produced from burning gasoline, wood, charcoal, propane, or other fuels. CO competes with oxygen to bind with Hb, forming COHb and leads to shifting the oxyhemoglobin dissociation curve to the left, reducing oxygen-carrying capacity, and oxygen release into the peripheral tissue. Tissue hypoxia due to CO induces vascular permeability and increased interstitial fluid accumulation with decreased circulating blood volume affecting multiple organs. Three clinical sequences consisted of symptoms consistent with CO poisoning, recent history of CO exposure, and elevated HbCO levels should be present in diagnosing CO poisoning. The current mainstay of CO poisoning treatment is high flow, normobaric (NBO) oxygen therapy administered as soon as possible.

Analisis Sifat Mekanik Komposit Serat Sabut Kelapa dengan Perlakuan Alkalisasi Etanol dan Filler Arang Tempurung Kelapa

Coconut trees are plants that are easily found in tropical areas such as Indonesia; therefore, natural products are abundant, but the use of waste from coconuts has not been processed into technological products. The aim of this study was to determine the differences in the variations in the volume fraction of fibers during tensile and impact strength testing. The variations in the volume fraction used were 5%, 10%, and 15% fiber, and the chemical treatment of the fiber was alkalized using 20% ethanol for 3 h of soaking. Composite manufacturing uses a hand layup method with random fiber orientation. The results of the research on variations in volume fraction of 5%, 10% and 15% obtained test values, in tensile testing such as maximum load obtained 32,844 kgf, 106.44 kgf and 105.59 kgf, maximum stress 6.0510 N/mm2, 16,893 N/ mm2 and 17.249 N/mm2, elongation breaking strain 0.8150, 0.3275 and 0.2617, breaking strain 1.4818 %, 0.5955 % and 0.4758 %, for the tensile test value the impact energy value was found to be 1.6 kgf, 2.3 kgf and 3.3 kgf and impact prices of 1.84 kJ/m2 , 2.45 kJ/m2 and 3.45 kJ/m2 . The high tensile and impact test results were due to mixing coconut fiber which had gone through ethanol alkalizing treatment with coconut charcoal powder to obtain high impact and tensile values.

Synergistic reduction on PM and NO source emissions during preheating-combustion of pulverized coal

The present research focuses on the synergistic source control of particulate matter (PM) and NOx formation from pulverized coal combustion. Comparative experiments of preheating-combustion and conventional combustion were conducted in a lab-scale high-temperature preheating-combustion furnace, and PM10 and NO were measured by an electrical low pressure impactor and a flue gas analyzer, respectively. The results of the experiment indicate that preheating-combustion has a significant reduction in PM10 (especially PM0.3 up to 37.51 %) and NO, which can achieve the synergistic control of PM10 and NO source emissions during the combustion process. The fragmentation in preheating-combustion was weaker compared to the conventional combustion. Meanwhile, the relatively weak preheating-combustion coal char oxidation reaction leads to a decrease in ultrafine mode PM yielded due to the inhibition on vaporization of mineral inclusions. The PM0.3/PM1 mass ratio of the preheating-combustion has a decreasing trend, implying an elevated yield of PM0.3-1 and a shift of the average PM1 particle size toward a larger particle size. Higher preheating temperature (Tp) presented the potential to further reduce NO formation, and the NO reduction efficiency increased from 46.59 % to 56.60 % when the Tp was increased from 1200 K to 1600 K. All our preliminary results throw light on the nature of synergistic source control of preheating-combustion PM and NO formation.

Exploration of the NO-char reaction pathway by in-situ DRIFTS and isotope gas tracing techniques

For NO abatement by carbon-based material (for example, char), many studies have been performed on the reactions between carbon and NO. Oxygen is believed to play a key role during the denitrification process: not only positive, but also negative. Some specific intermediates are worth investigating, and reaction routes are needed to be clarified in order to reveal and explain the mechanism of the concerned reactions. To account for the reaction scheme, chemical evolution information of both solid surface side and gaseous side are collected and analyzed by means of in-situ DRIFTS analysis and isotopic gas tracing, respectively. In combination with experimental results of the NO-char reaction in a fixed bed, possible reaction pathway is proposed. The in-situ DRIFTS analysis shows that C(N) and thermodynamically active C = O complexes are produced during NO adsorption on coal char. The presence of O2 promotes the chemisorption of NO molecules. Oxygen combines with carbon to generate not only thermodynamically stable C-O complexes but active C = O complexes. Step response experiments using isotope gas tracing technique demonstrate that CO and CO2 are produced by C = O desorption and the combination between C-O and C = O complexes, respectively. N2 is generated by the reaction of C(N) complexes on the coal char surface with NO molecules in gas phase. The stable C-O complexes promote NO adsorption and dissociation by reaction with C = O complexes and subsequently producing new active sites.

The Effect of Incubation Time and Drainage pH on the Immobilization of Copper in Post Coal Mine Soil Using Sumatera Brown Coal Char

Post coal mine (PCM) activities pose significant environmental challenges. Soils affected by PCM often exhibit increased acidity and elevated levels of heavy metals. In the case of Sungai Buluh PCM in the Jambi Province, Indonesia, copper (Cu) levels in the soil reach 94.79 mg kg-1, surpassing the Indonesian standard of 40 mg kg-1. Sumatera brown coal (SBC), typically is not considered as fuel due to its properties, offers a cost-effective solution for Cu immobilization in such soils. In this study, SBC was subjected to pyrolysis at 400°C for 1 h, sieved through a 10-mesh sieve, and characterized using SEM and FTIR. The soil-char mixture consisted of 250 g of soil and 25 g of char (9:1 ratio), while a control group included 250 grams of soil with no char. The soil's pH significantly influenced Cu adsorption by SBC char. Cu immobility by SBC char was highest at pH 5, with an efficiency of 66.67% from pH 1 to 5. Over a 4-week period, the mobility of Cu in soil containing 10% char decreased by 36.36%. Pseudo-first-order kinetics yielded R2 values of 0.750 and 0.979 for 0% and 10% char additions, respectively. To inform future research on SBC char's potential for soil amendment, exploring the properties of SBC char produced at different pyrolysis temperatures is advisable. This information can aid in the development of char furnaces with appropriate technology to efficiently produce large quantities of effective SBC char. Additionally, determining optimal incubation times can help predict the frequency of char application in various regions.

In-situ Raman spectroscopy study on coal pyrolysis and subsequent char low temperature oxidation and gasification

Thermal conversion is pivotal for clean and efficient coal utilization. Evolution of solid structure profoundly affects the gasification mechanism. However, in-situ study on coal structure evolution during gasification is limited. In this study, in-situ Raman spectroscopy was used to investigate the carbon structure evolution during thermal conversion. Results revealed two stages in coal pyrolysis: polycondensation and aromatic ring fusion. During polycondensation, numerous side chain groups break, while aromatic compounds condensed and rings fused in the aromatic ring fusion stage, increasing molecular size. In char gasification, larger particles required more time to achieve stable shrinkage, thus delaying coal char graphitization process. Low temperature oxidation led to decreased order due to oxygen-containing structure formation, evolving into a graphite-like structure as disordered carbon diminished. In addition, oxygen-containing groups acted as active oxidation sites. The insights into real-time structure evolution enhance understanding of the particle behavior during thermal conversion of coal.

Flash-pyrolyzed coal char as a high-performance anode for sodium-ion batteries

This work explores a novel approach for improving the sodium-ion battery performance of coal char using flash pyrolysis and an ether-based electrolyte. Coal char is an ultra-low cost hard carbon with promising application as an anode material in sodium-ion batteries. During flash pyrolysis, char is heated at 1000 °C/s in a drop-tube furnace to create a highly-irregular structure. The larger d-spacing and smaller closed micropore diameter of flash-pyrolyzed char increases anode capacity compared to traditional slow-pyrolyzed char electrodes. The sodium-ion battery anode performance of flash-pyrolyzed char is further improved using an ether-based electrolyte in place of the traditional ester-based electrolyte. Performance improvements include greater initial Coulombic efficiency (58% in ester- vs. 64% in ether-based electrolyte) and improved specific capacity in an ether-based electrolyte. Overall, the combination of flash pyrolysis and ether-based electrolyte increases the sodium-ion battery discharge capacity of coal char by over 50%, from 72.5 mAh g−1 (slow-pyrolyzed char in ester-based electrolyte) to 109.4 mAh g−1 (flash-pyrolyzed char in ether-based electrolyte) (50 mA g−1 discharge rate). The results highlight improvements that can be realized through flash pyrolysis of coal char for battery applications and the numerous processing advantages of flash vs. slow pyrolysis.