Coal Liquefaction Research Articles

Multistep Fractionation of Coal and Application for Graphene Synthesis.

Despite its complex structure, coal has shown to be a promising precursor for graphene synthesis by chemical vapor deposition (CVD). However, the presence of heteroatoms and aliphatic chains in coal can lead to defects in the graphene lattice, preventing the formation of pristine graphene layers. Therefore, the goal of this study was to formulate a multistep coal fractionation scheme to extract and characterize the most aromatic fractions and explore their potential as graphene precursors. The scheme consisted of direct coal liquefaction under different conditions, Soxhlet extraction with heptane then toluene, and preparative liquid chromatography on silica gel using heptol solutions with different heptane/toluene ratios. The fractions obtained by this process were analyzed by proton nuclear magnetic resonance, thermogravimetric and elemental analyses, and automated SAR-AD (saturates, aromatics, resins-asphaltene determinator) separations. This characterization allowed the identification of two aromatic fractions with and without heteroatoms, which were subsequently used for graphene synthesis by CVD on nickel and copper foils. Raman spectrometry revealed that both fractions primarily formed defect-free multilayered graphene with approximately 11 layers on nickel due to the high solubility of carbon and the defect-healing effect of nickel. On the other hand, these fractions generated amorphous carbon on copper due to the high solubility of hydrogen in copper, which competed with carbon. Molecules in the more aromatic heteroatom-free fraction still contained alkyl pendant substituents and did not share the same planarity and symmetry to form defect-free graphene on copper. Thus, the quality of graphene was governed by the substrate on nickel and by the precursor quality on copper. When deposited directly on lacey carbon-coated copper grids of a transmission electron microscope, the heteroatom-free fraction gave rise to much larger graphene domains. The presence of heteroatoms promoted the formation of small self-assembled agglomerates of amorphous carbon.

Comparative assessment of n-butanol addition in CTL on performance and exhaust emissions of a CI engine

Coal to liquid (CTL) is a diesel alternative fuel based on Fischer-Tropsch (FT) process, which has shown promising application value. Besides, as an oxygenated biofuel with high oxygen content and volatility, n-butanol can be blended with hydrocarbon fuels to improve engine performance. This study aims to investigate the effects of CTL/n-butanol blends on the performance of the compression-ignition (CI) engine, and to reveal the influence of combustion boundary conditions such as n-butanol blending ratio, the start of injection (SOI), and exhaust gas recirculation (EGR) on the combustion and emissions characteristics. The results show that blending n-butanol with CTL is beneficial to improve the fuel-gas mixture distribution in the cylinder, and the premixed combustion ratio (PCR) increases by 13.66% as the energy ratio of n-butanol increases to 30% (B30) compared with the pure CTL. CTL/n-butanol blends make particulate emission tend to be shifted towards nucleation mode and the particulate mass emission significantly reduced, especially the particulate mass of B30 reduce by 68.6%; meanwhile, the NOx emission shows an upward trend. Compared with n-butanol blended, adjusting the SOI impacts NOx emissions significantly, while its influence on the indicated thermal efficiency (ITE) and particulate emissions is relatively slight. Moreover, through the synergistic control of n-butanol addition and EGR, the trade-off relationship between NOx and particles is mitigated.

Effect of physical hardening on low temperature performance of DCLR modified asphalt

This study aims to investigate the effect of physical hardening on the low temperature performance of direct coal liquefaction residue (DCLR) modified asphalt. The extended bending beam rheometer (EBBR) method was used to evaluate the low temperature performance of DCLR modified asphalt with benzaldehyde, silane coupling agent and xylene compatibilizer. Meanwhile, the microstructure and morphology of DCLR modified asphalt before and after physical hardening were quantitatively characterized by atomic force microscope (AFM) and image processing software. In this study, the physical hardening was performed by placing the DCLR modified asphalt at low temperature conditions for a certain time. The test results show that as the conditioning temperature decreased and the conditioning period increased, both low temperature grade loss and hardening rate of asphalt increased, indicating that the low temperature performance deteriorated. Compared to the room-temperature conditions, the total number of “bee-structures” of DCLR modified asphalt under low temperature conditions were less, but the shape of a single “bee-structure” became larger and longer. The compatibilizers hindered the growth of “bee-structure”, which demonstrated that the compatibilizers could improve the low temperature performance of asphalt. The three compatibilizers had different effects on low temperature performance of DCLR modified asphalt. Among them, the silane coupling agent was the most effective, followed by benzaldehyde and xylene.

Characterization of humic acids produced from fungal liquefaction of low-grade Thar coal

Fungal liquefaction of coal is a promising technology to convert low rank coal into value-added products such as humic acids (HAs) that are extensively used as fertilizer. Use of Pakistani Thar lignite for humic acid extraction can promote agriculture industry in Pakistan. In this study, fifty-five fungal strains were isolated from Thar lignite and screened for their lignite solubilization efficiency. Isolates M13 and MI exhibited highest capacity for lignite solubilization and HA was extracted with 67.4 ± 4.3 percent (w/w) yield. Elemental analysis showed increased nitrogen (0.72–1.39 percent) and oxygen (41.7–48 percent), and decreased carbon (51.8–46.1 percent) and sulphur (1.18–0.73 percent) contents in bio-extracted HA (bHA) compared to chemically extracted HA (cHA). UV/Vis spectroscopy showed increased E4/E6 value from 5.6 ± 0.39 (cHA) to 6.28 ± 0.35 (bHA) indicating reduced molecular mass and aromaticity and increased bioactivity of molecule. FTIR analysis also confirmed these results. HPLC analysis of bHA and cHA showed typical choromatogram of humic acids. Enzyme activity staining indicated the presence of fungal cellulase and xylanase on SDS-PAGE gel. The degradation of lignite macromolecules by lignin degrading fungi is a complex process dependent on alkaline substances, chelators, surfactants and extracellular fungal enzymes.

A Study on Standardization of Security Evaluation Information for Chemical Processes Based on Deep Learning

Hazard and operability analysis (HAZOP) is one of the most commonly used hazard analysis methods in the petrochemical industry. The large amount of unstructured data in HAZOP reports has generated an information explosion which has led to a pressing need for technologies that can simplify the use of this information. In order to solve the problem that massive data are difficult to reuse and share, in this study, we propose a new deep learning framework for Chinese HAZOP documents to perform a named entity recognition (NER) task, aiming at the characteristics of HAZOP documents, such as polysemy, multi-entity nesting, and long-distance text. Specifically, the preprocessed data are input into an embeddings from language models (ELMo) and a double convolutional neural network (DCNN) model to extract rich character features. Meanwhile, a bidirectional long short-term memory (BiLSTM) network is used to extract long-distance semantic information. Finally, the results are decoded by a conditional random field (CRF), and then output. Experiments were carried out using the HAZOP report of a coal seam indirect liquefaction project. The experimental results for the proposed model showed that the accuracy rate of the optimal results reached 90.83, the recall rate reached 92.46, and the F-value reached the highest 91.76%, which was significantly improved as compared with other models.

Strength analysis of noncovalent interactions between lignite and direct liquefaction solvents: A joint study of DFT calculations and swelling ratio determination

Noncovalent interactions have achieved extensive attentions in thermal conversion of low rank coal, but have been little studied in direct coal liquefaction (DCL). In order to investigate strength of noncovalent interactions (hydrogen bonds and π–π stacking) between lignite and DCL solvents, experimental methods and DFT (density function theory) calculations were utilized. Aromatic components in industrial recycled solvents have been selected, including tetralin, 1,2–dihydronaphthalene (DHN), indane, 1–methylnaphthalene, naphthalene, indene and benzene. On one hand, total strength of noncovalent interactions between those aromatic components and lignite were integrally evaluated by swelling ratio determination. On the other hand, Spatial distribution and strength of noncovalent interactions were investigated by RDG (reduced density gradient) analysis, CVB (core–valence bifurcation) index and LOLIPOP (localized orbital locator integrated pi over plane) index, respectively. Overall, addition of DHN, indane and benzene resulted in significant swelling of lignite. Swelling of lignite in benzene and others (DHN and indane) was enhanced by stronger OH–π hydrogen bonds and π–π stacking, respectively. By conjoint study of swelling ratio and DFT calculations, both hydrogen bonds and π–π stacking play crucial roles in swelling of lignite. Adjustment of noncovalent interactions should be taken into account during design of DCL solvents, based on correlations between noncovalent interactions and structural characteristics of aromatic components.

Study on the transformation characteristic of heteroatoms during liquefaction of Naomaohu coal

In this work, Naomaohu coal was used for direct liquefaction. The conversion and oil yield as a function of hydrogenating temperature were investigated, and the transformation characteristics of heteroatoms in raw coal and liquefaction products were clarified. The results showed that Naomaohu coal presented high liquefaction performance even under lower initial pressure of 2 MPa. The conversion and oil yield could reach 69.6% and 55.3%, respectively, at a pressure of 2 MPa and 400°C. Gas chromatography-mass spectrometry and gas chromatography-atomic emission spectrometry were combined to analyze the products. It was found that the weak bond structure containing heteroatoms was easier hydrogenated to fracture and removed in the form of H2S, NH3, H2O, etc. The sulfur-containing compounds in liquefied products were mainly thiophene and thiophene homologues. The content of nitrogen-containing compounds was trace and mainly consisted of nitrogen heterocyclic compounds. The oxygen-containing compounds in liquefied oil were dominantly phenols and their homologues. The heteroatoms in the aromatic structure would generate more stable heteroatom-containing compounds in the liquefaction residue via the free radical polycondensation reaction.

Direct liquefaction performance of sub-bituminous coal from Hefeng by solid super acids and pyrolysis kinetic analysis of the corresponding residue

Highly active, recyclable, and reusable supported super-acid catalyst is of great significance for improving coal liquefaction performance and liquefaction conditions and realizing comprehensive utilization of coal resources. Solid super-acid catalysts were prepared by impregnation method with trifluoromethanesulfonic acid (TFMSA) supported on different carriers (ZrO2, Al2O3, SiO2, and ZSM-5). Hefeng sub-bituminous coal (HFSB) was used as raw material to investigate the liquefaction effect of the catalysts. Composition, structure, acidity property of the catalysts were analyzed by EDS, XRD, and NH3-TPD methods, and direct coal liquefaction performance of the catalysts was performed, and TG-DTG characterization was used to evaluate the pyrolysis behavior of the liquefaction residue. Results showed that activity of the four supported solid super-acid catalysts was followed by TFMSA/ZrO2, TFMSA/ZSM-5, TFMSA/Al2O3, and TFMSA/SiO2, with coal conversions of 84.20 %, 78.40 %, 76.67 % and 73.23 %, and oil yields of 67.16 %, 62.53 %, 61.15 %, and 58.41 %, respectively. The Coast-Redfern method was used to analyze the pyrolysis kinetics of the four coal liquefaction residues (R-ZrO2, R-ZSM-5, R-Al2O3, and R-SiO2). Results presented that, in low temperature range (200−530 ℃), except R-SiO2, the pyrolysis process of residues conforms to the third-order reaction. And in high temperature range (530−850 ℃), the four-order reaction is more suitable for the four residues. The pyrolysis activation energy of R-ZrO2 is lower at low temperature region (16.822 kJ/mol), while R-Al2O3 presents lower activation energy at high temperature range (45.494 kJ/ mol).

Evolution and mechanism of a new index liquid-gas ratio (LGR) in coking of coal blending

Direct coal liquefaction residue (DCLR) was blended with five bituminous coals to prepare crucible coke in the laboratory. A new index liquid-gas ratio (LGR) was defined to quantify relative amounts of liquid phase and gas phase during coking. Great attention was paid to the early stage of coking (400−600 ℃) and then LGR was modified to LGR(t). Relationships and mechanism between LGR, LGR(t) and coke strength were investigated and summarized. Results showed that when high caking property coal ratios was inadequate (< 60 %), the higher LGR was, the larger coke strength was. When high caking property coal ratios was over 60 %, LGR was over 37 mm and coke strength could be guaranteed. Besides, polynomial fitting results of LGR and CSR* showed that coke strength increased sharply and then decreased slightly when LGR increased from 20 to 40 mm. The optimal LGR of coal blends was 37 mm and rational LGR range was from 33 to 40 mm. It was also found that LGR(t) needed to be at least 90 mm at the peak temperature during the early stage of coking. In addition, DCLR ratio in blending system needed to be controlled within 5%. Otherwise, the content of gas was inadequate enough to squeeze large amounts of metaplast into holes at the temperature range 400–430 ℃. Finally, it was concluded that high quality coke could be obtained with two requirements: high caking property coal ratios was abundant (> 60 %) and the content of gas druing coking matched the content of metaplast (rational LGR and LGR(t)).

Kinetic modelling of low temperature direct coal liquefaction: Consideration of dynamic catalyst activity

A kinetic model for direct coal liquefaction at low temperature in the presence of a magnetite nano-catalyst was developed. The model took into account the iron oxide catalyst transformation into its active state as well as the process of reactive dissolution of coal at the reduced temperatures. The validity of the model was tested by performing a regression on experimentally obtained data for the direct coal liquefaction process. The experiments were performed in a high-pressure batch reactor, with medium to low ranking coal, using synthesised magnetite nano-catalysts and within the temperature range of 240 °C to 320 °C. This temperature range is known to be below that required for thermolysis of the coal. The model was able to qualitatively capture the general trends of the experimental data. The regression indicated that the depolymerisation reactions of the dissolved moieties directly into key products occur more rapidly than the reactions of key product groups, which is a typical occurrence in lower rank coals.

Hydroliquefaction kinetics of coal-derived preasphaltenes catalyzed by FeS and S

Hydroliquefaction behavior of preasphaltenes, derived from direct coal liquefaction, was carried out in a 30 mL autoclave with FeS + S catalyst and tetralin at initial hydrogen of 5.0 MPa, residence time of 0–60 min and reaction temperature of 380–440°C in order to optimize the conditions of direct coal liquefaction and improve oil yield. The products distribution and kinetic parameters of preasphaltenes catalytic hydroliquefaction were investigated. A new kinetic model was established to simulate the preasphalteneshydroliquefaction catalyzed by FeS + S catalyst using lump kinetic model. It was found that preasphaltenes were hydroliquefaction into asphaltenes and char directly, and then asphaltenes were hydrocracked into oil + gas products. Regressive reactions of preasphaltenes to char and asphaltenes to preasphaltenes occurred at higher temperatures. Higher temperature and longer time were favorable for increasing the conversion of preasphaltenes and the oil + gas yield. The hydroliquefaction of preasphaltenes under 440°C and 60 min reached 79.45% with 34.7% of oil + gas yield. The hydroliquefaction conversions calculated from the model agreed well with the experimental data, and the activation energies ranged within 50–245 kJ/mol.

A comparative study on direct liquefaction of two coals and hydrogen efficiency to the main products

To improve the performance of megaton direct coal liquefaction (DCL) technology that has been practiced in China since 2008 and to develop a better technology that can be operated at milder conditions with high efficiency, this work studies coal conversion (XC), products yield (Yi) and hydrogen consumption (RH) of SW coal (H/C = 0.75) used in the megaton plant and NMH coal of a higher H/C ratio (0.97) in tetralin and a temperature range of 380–455 °C. The experiments were carried out in fast heating high-throughput micro reactors and the dependencies of XC and Yi on temperature, time, and RH are studied. The results show that the XC-RH and Yi-RH relations are coal dependent but not temperature dependent in the temperature range of 380–440 °C. The kinetics modeling indicates that NMH contains more mobile fractions than SW and appreciable amounts of coals react in the 1 min heating-up period. The rate constants of coal to each product follows the order of asphalt (AS) > oil (O) > organic gas (OG), while the activation energy and H consumption to each product follows a reverse order.

Co‐Ni‐P‐B catalyzed hydroformylation of long linear α olefins

AbstractBACKGROUNDAs indirect liquefaction of coal has been carried out in megaton scale, extension of the Fischer‐Tropsch synthesis products has received renewed interest. Hydroformylation provides a way for the transformation of alkenes to aldehydes. Homogeneous rhodium complex catalysts are efficacious but expensive and not easy to recover and reuse. Heterogeneous catalysts are desired to enable their easy separation. Amorphous four‐component non‐precious metal catalysts were prepared using facile reduction and their activity toward hydroformylation of long linear α olefins was investigated.RESULTSObtained Co‐Ni‐P‐B presented uniform nanoparticles that were well‐dispersed Co with more electrons, attributing to isolation and electron transfer among the four components. The Co, Ni, P, and B were in both atomic states and oxidation states. The Co in Co‐Ni‐P‐B was shown to be electron‐enriched with enhanced catalytic activity. Co‐Ni‐P‐B displayed good catalytic activity for hydroformylation of linear C6, C8, C10, or C12 α olefins, and the highest activity for 1‐octene. The conversion of 1‐octene and the selectivity of C9 aldehydes reached 99.62% and 96.30%, respectively. The ratio of nonanal to isononanal was 1.44. The selectivity for isomeric products was 3.70%. There existed an appropriate four‐component ratio for hydroformylation of 1‐octene owing to synergistic effects among the Co, Ni, P, and B. Co‐Ni‐P‐B exhibited good reusability.CONCLUSIONAmorphous four‐component Co‐Ni‐P‐B prepared by facile reduction showed good catalytic performance toward hydroformylation of long linear C6, C8, C10, or C12 α olefins due to synergistic effects among the Co, Ni, P, and B. © 2021 Society of Chemical Industry (SCI).

Development of a reduced mechanism of a three components surrogate fuel for the coal-to-liquid and diesel combustion simulation

In order to explore the difference between coal-to-liquid (CTL) and diesel in the combustion and the pollutant formation process, in this study, a reduced mechanism of the CTL and diesel surrogate fuel for the 3D computational fluid dynamics (CFD) simulation is developed. According to the physicochemical properties, the CTL surrogate fuel is determined to be composed of 88.99% n-dodecane and 11.01% iso-octane by mass. Using a series of reduction methods including Directed Relation Graph with Error Propagation, Directed Relation Graph, Directed Relation Graph with Path Flux Analysis and isomer lumping, the CTL surrogate reduced mechanism with 132 species and 873 reactions is obtained. For the diesel surrogate fuel, 74.31% n-dodecane and 25.69% iso-octane by mass are selected. By coupling the m-xylene sub-mechanism derived from a jet fuel surrogate to the CTL reduced mechanism, the CTL and diesel surrogate reduced mechanism with 146 species and 924 reactions is developed. The sensitivity analysis is conducted to optimize the rate parameters and improve the accuracy of predicting the ignition delay (ID). The CTL and diesel reduced mechanism is then validated against experimental data on fundamental reactors and is confirmed to well reproduce the IDs, the laminar flame speeds and the species profiles for a wide range of conditions. Finally, the 3D CFD validations on the compression ignition (CI) engine are conducted. All the errors of key combustion parameters are lower than 25%, demonstrating the strong capability of the reduced mechanism to predict the conventional CI combustion of CTL and diesel at medium loads.

Evaluation of black carbon source apportionment based on one year's daily observations in Beijing

Combustion-derived black carbon (BC) is increasingly recognized as a significant pollutant that can have adverse effects on the atmospheric environment, human health, and regional climate. Fossil fuel combustion is the main source of BC, yet understanding of the relative contributions to BC from coal and liquid fuel combustion remains incomplete. Moreover, few studies have assessed the relative contributions based on long-term continuous daily field observations. This study adopted a Bayesian model of a three-dimensional array of a stable carbon isotope and the ratios of non-sea-salt K+ to BC and ΔBC/ΔCO of one year's daily observations (from September 1, 2017 to August 31, 2018) to constrain source apportionment of BC in Beijing (China). Results showed that both the BC and the carbon isotope concentrations exhibited strong seasonal variability, and that the annual BC concentration has decreased significantly in recent years. The Bayesian model results also revealed that the relative contributions from the combustion of coal, liquid fuel, and biomass were 42% ± 18%, 42% ± 18%, and 16% ± 11%, respectively, with a larger contribution from coal (liquid fuel) combustion in winter and spring (summer and autumn). The seasonal variation of source appointment was attributed to local and regional fuel combustion coupled with meteorological conditions. With increasing PM2.5 level, the BC concentration derived from biomass burning increased fastest, followed by that derived from coal combustion. But concentration of secondary inorganic ions increased faster than BC as PM2.5 increased.

Ignition characteristics of an alternative kerosene from direct coal liquefaction and its blends with conventional RP-3 jet fuel

Jet fuel from direct coal liquefaction (DCL) is an important alternative kerosene. The study of its ignition characteristics is not only critical for the development of combustion kinetic models, but also is valuable to evaluate its compatibility in current aeroengines. This work reports the first experimental study on autoignition characteristics of a jet fuel from DCL and its blends with conventional RP-3 jet fuel. Ignition delay times (IDTs) for DCL fuel, RP-3 and their blends are measured by using heated shock tube facility over a wide range of conditions. The studied pressure is 2 and 10 bar, the equivalence ratios are 0.5, 1.0 and 2.0, and the temperature range is from 920 K to 1700 K. The influence of temperature, pressure, and equivalence ratio on the IDTs is investigated. Surrogate models for the three fuels and detailed kinetic mechanism are developed to describe the combustion chemistry. Comparison between the predictions using the detailed kinetic models and the experimental data shows that the developed models exhibit acceptable performance versus the measured IDTs. Brute force sensitivity analyses are carried out to identify the key reactions controlling the ignition characteristics. The experimental data set and kinetic models extend our understanding of the ignition characteristics of alternative jet fuels.

Investigation on chemical structure and hydrocarbon generation potential of lignite in the different pretreatment process

Combined with the analysis of FT-IR, lignite was treated by conventional flue gas (FTD), hydrothermal (HTD), and tetralin solvent thermal pretreatment (TTD) at different temperatures. A series of infrared parameters were obtained, and the evolution of chemical structure and hydrocarbon generation potential for lignite were studied. The results showed that the HTD, TTD and FTD processes reduce the water holding ability of lignite, and in general, the order of the dewatering effect is HTD > TTD > FTD. The FTD process promotes more efficient the increase of carbon content and energy density, and the upgraded coal likely to be suitable as power fuel. For lignite, the hydrogen-enrichment parameters are not an effective means to predict hydrocarbon generation potential, because the structural characteristics are not dominant during the process of hydrocarbon generation. The aromatization occurred during the FTD, HTD, and TTD processes, and has an important contribution towards enhancing the aromaticity. The order of aromatization of lignite for the three pretreatment processes is FTD > HTD > TTD. Conversely, the upgraded coal achieved by TTD process maintains the relative integrity of organic structure and high reactivity of lignite. HTD and TTD processes improve the H/C atom ratio of lignite, which provides more hydrogen free radicals to produce chemical products. Thus, the upgraded coal is suitable as feedstock of coal pyrolysis and liquefaction. Moreover, the upgraded coal achieved by TTD process retains high reactivity and relative integrity of organic structure compared with the HTD process. Thus, it has a much better chance of producing value-added chemical products.

Residues characteristics and structural evolution of Naomaohu coal during a mild direct liquefaction process

Direct coal liquefaction (DCL) is an important way of coal conversion and is important to the global energy industry. In this paper, a typical liquefied coal–Naomaohu coal (NMHC)–was liquefied under mild conditions (400 °C, initial H2 pressure of 3 MPa), and a NMHC conversion of 90.6% was obtained with an oil+gas yield of 65.1%. In the DCL process, the solid particles of coal and its residues are not only reactants but also carriers of catalysts of DCL. To study the structural characteristics of these residues, the reaction mixture was extracted with n-hexane and tetrahydrofuran (THF), separately, yielding n-hexane insoluble residues (ReHEIS) and THF insoluble residues (ReTHFIS). Several patterns of the reaction progresses were identified. First, the particle sizes of ReHEIS and ReTHFIS have a decreasing trend, and the particle surface becomes loose and porous while raw coal has a relatively flat surface. Second, most of the aliphatic structure and some small aromatic compounds can gradually split off from coal skeleton structure, and the condensation degree of aromatic clusters in residues increases with the aromatic condensation degree of ReTHFIS being higher than that of ReHEIS. Third, the contents of carbonyl carbon and oxygen-attached carbon decrease while methylene chain and side chain of aromatic clusters are broken. Lastly, the aromatic structure of ReTHFIS becomes regular, and the graphitization degree increases, while the pyrolysis rate slows down. These results of element analysis show that the H/C of ReHEIS is larger than that of ReTHFIS, which implies that preasphaltene and asphaltene are relatively rich in hydrogen.

Experimental and numerical investigation on the load stability of coal cargoes during marine transport

During marine transport of coal commodities, cargo slip or liquefaction failure scenarios within the hold may occur under cyclic ship motions. The resulting cargo shift affects the vessel stability, and subsequently endangers goods and crews on board the vessel. This study aims to investigate the coal cargo stability under marine transport conditions. A suite of six coal samples was selected to undertake a series of undrained cyclic triaxial tests to investigate their liquefaction resistance. Results were subsequently compared to the liquefaction threshold advised by International Maritime Organisation. It was suggested that finer coals were observed to be more susceptible to liquefaction. In addition, discrete element modelling of the coal cargoes was conducted to study the cargo slip susceptibility. Calibration was performed to ensure materials modelled in the numerical program reflected the physical behaviours. Results indicated coarser coal samples with lower moisture contents exhibited cargo slip failures under nominated rolling ship motion. Nevertheless, resulting centre of gravity shift from cargo slip exhibited negligible effect on the cargo stability. Outcomes of this study provided important safety guidelines on marine transportation of coal commodities.

An approach for upgrading lignite to improve slurryability: Blending with direct coal liquefaction residue under microwave-assisted pyrolysis

As the composition of direct coal liquefaction residue (DCLR) is complex and difficult to handle, more importantly its dielectric properties are excellent, it is used as consumable wave-absorbents to enhance the microwave pyrolysis of lignite for slurryability improvement. The effects of the different additions of DCLR on the evolution of pyrolysis products were studied by using gas chromatography, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and low-temperature N2 adsorption analysis. The results indicated that microwave-assisted pyrolysis with DCLR was a promising method for improving slurryability of lignite and an effective method for utilizing DCLR. The introduced DCLR accelerated the heating rate of the process of microwave upgrading lignite, facilitating the decomposition of active oxygen-containing functional groups and aliphatic hydrocarbons and then their transformation into stable ether groups and aromatic structures. In the meantime, it was converted into gaseous products, mainly composed of H2, CO, and CH4, and solid products with high quality. Additionally, the cyclization and aromatization of organic structures were improved, as well as the order degree of aromatic systems, especially with 12 wt% of DCLR added. Furthermore, the existing and newly formed structures of micropores and mesopores in the upgraded lignite (UL) were remarkably reduced with the increase of DCLR contents. The re-absorption capacity was dramatically reduced and the slurryability of UL was improved as a result of the changes in chemical properties and pore structures. The maximum solid concentration of lignite water slurry (LWS) increased from 41.73 wt% to 65.42 wt% with lower pseudo-plasticity and static stability.