Direct Liquefaction Research Articles

Direct liquefaction behavior of Shenhua Shangwan coal under CO containing atmosphere

Direct coal liquefaction (DCL) under CO or syngas atmosphere is beneficial to reduce the cost of hydrogen production. Effects of CO on liquefaction process of Shangwan coal were investigated by comparing the liquefaction behavior in three atmospheres of CO, H2, and N2. Then, effects of different CO/H2 ratios and catalysts on the liquefaction process in syngas were investigated. The results indicated that the oil yield under CO atmosphere reached 43.1%, which was 4.2% lower than that under H2, but 10.2% higher than that under N2. The liquefaction performance was further improved by adding the Shenhua 863 catalyst. It is analyzed that CO promoted liquefaction in two ways: water-gas shift reaction and the reaction between CO and organic structures of coal. Through characterization of the products by GC-MS and FT-IR, it was found that CO makes benzenes, aliphatics, and oxygen-containing compounds in liquefied oil simultaneously increased. The effect on functional groups and free radicals concentration in the solid products was not obvious. The experimental results under syngas showed that the highest oil yield, 57.4%, can be obtained in DCL with 20% CO syngas, and further improved by increasing moisture content of coal appropriately. In addition, the Shenhua 863 catalyst had a good catalytic effect on the liquefaction process and also water-gas shift reaction.

Production characteristics in initial pyrolysis of lignin based on reactive molecular dynamics simulations

Abstract Carbonization, direct liquefaction, and gasification, which are based on pyrolysis reactions, have been proposed as efficient technologies for energy recovery from biomass resources. However, modeling pyrolysis reactions of biomass with complex molecular structures is challenging, and numerical analysis methods that consider product compositions have not yet been established. In this study, molecular dynamics simulations were performed using LAMMPS, with the force field parameterized using ReaxFF. A molecular model based on Adler softwood lignin was created. The atomic trajectories were analyzed to identify the products of the pyrolysis process, and changes over time in inorganic gas, organic gas (C1-C4), light tar (C5-C14), heavy tar (C15-C39), and char (C40+) during the initial pyrolysis of lignin were investigated. The distribution of compositions formed and the formation behavior of typical low-molecular-weight components (such as formaldehyde and methanol) and inorganic gases from lignin were evaluated. The characteristics of the products in the initial pyrolysis of lignin, as analyzed from the molecular dynamics simulations, were based on the functional groups in the molecular model of lignin. Furthermore, similarities with the product compositions identified in experiments were also confirmed.

Turning coal hydrogenation liquefaction residue into high conductivity carbon black with magnesium citrate-assisted steam activation followed by high temperature treatment

The high conductivity carbon black was prepared using coal hydrogenation liquefaction residue as raw material, through a combination methods of solvent extraction purification, magnesium citrate-assisted carbonization, steam activation, and high-temperature treatment. The effects of carbonization and activation process parameters, heat treatment temperatures, and other factors on the microstructure, specific surface area, degree of graphitization, and conductivity of the carbon black were studied. The coal direct liquefaction residue was firstly purified using a xylene and tetrahydrofuran solution with a volume ratio of 1:1 by centrifugal separation method to obtain coal liquefaction asphalt. Then, the coal liquefaction asphalt was mixed with magnesium citrate in a mass ratio of 3:7 and ball-milled for 90 min. After carbonizing at 950 °C for 120 min, magnesium ions were leached out with hydrochloric acid. The obtained sample was activated with steam at 900 °C for 100 min and then underwent high-temperature treatment at 1500 °C under a N2 atmosphere for 120 min. The microstructure of the conductive carbon black exhibited an irregular blocky structure with an average particle size of 2–10 μm. The specific surface area of carbon material was 579.69 m2/g, with the pore distribution predominantly microporous, accounting for 69.81 % of the total pore volume. It featured a higher degree of graphitization (ID/IG=1.06) and fewer surface oxygen-containing functional groups compared with coal direct liquefaction residue. Electrochemical testing showed that the electrical resistance of the carbon material was only 1.55 Ω, and the reversible capacity under a current density of 1 A/g was 96 mAh/g, which are superior to those of the existing commercial conductive carbon black. The microporous structure and higher degree of graphitization facilitate efficient electron transmission, while the lower content of surface oxygen functional groups effectively reduces electron transfer resistance. This work offers new insights into the structural design and performance enhancement of coal liquefaction residue-derived conductive carbon black functional materials. Furthermore, it has significant implications for the future development of conductive carbon black in energy saving and energy storage.

THE IMPORTANCE OF BIOETHANOL AS AN ENVIRONMENTALLY CLEAN FUEL

This article is a review based on literature sources. The production technology and areas of application of bioethanol, as well as ways to intensify the production of alcohol obtained from these natural sources, are analyzed. One such method is biomass liquefaction. Modern technologies for converting biomass into valuable biofuels were studied. Common biomass liquefaction technologies are indirect liquefaction and direct liquefaction. Direct biomass liquefaction involves converting biomass into bio-oil, and the main technologies are hydrolytic fermentation and thermodynamic liquefaction. Based on thermodynamic liquefaction, it can be divided into fast pyrolysis and hydrothermal liquefaction. In addition, this review provides an overview of the physicochemical properties of biodiesel and common methods for its processing. Keywords: bioethanol, yeast, natural food waste, purchasing biofuel.

Preparation of high-performance bitumen carbon-based microwave absorbing materials from different coal bitumens toward efficient treatment of industrial waste bitumen

The increasing development of communication technology and electromagnetic pollution have accelerated the research and optimization of electromagnetic microwave absorbing materials. There are few studies and reports on the creation electromagnetic microwave absorbing materials from industrial waste, despite the abundance and promise of research preparing of microwave absorbing materials utilizing sustainable resources from biomass. Herein, we prepared carbon-based microwave absorbing materials GCB-800, HTCB-800, and CDLB-800 using three different industrial solid waste bitumens, namely, coal direct liquefaction bitumen, high-temperature coal bitumen, and globular coal bitumen, as raw materials by using the thermal activation method. Due to the excellent porous carbon skeleton structure and the Fe2O3 contained in its internal ash after the heat treatment, which enhances the internal dielectric properties, the CDLB-800 was found to perform very well at the filler amount of 10 wt% obtained minimum reflection loss (RLmin) is −52.41 dB at 10 wt% filler and matched thickness d = 2.1 mm, and the effective absorption bandwidth (EAB) is 4.88GHz, with 87.14% absorption for X-band in the 2-18GHz. This work not only promotes the development of the comprehensive utilization of solid waste in this field, effectively reduces the burden of solid waste on the environment, but also points out the direction for the development of microwave absorbing materials in the future.

A Study on the Hydro-Liquefaction Kinetics of Shengli Lignite during the Heating-Up and Isothermal Stages under Mild Conditions

Studying the hydro-liquefaction kinetics of lignite contributes to optimizing the mild liquefaction process for lignite. In this paper, the direct liquefaction performance of Shengli lignite (SL) was investigated using a H2/THN system with 4 MPa of initial pressure, and reaction kinetic models were established for the heating-up stage and the isothermal stage. The result showed that the liquefaction performance of the SL was excellent, with a conversion of 62.18% and an oil and gas (O + G) yield of 29.88% at 698.15 K. After one hour of reaction, the conversion and O + G yield were 94.61% and 76.78%, respectively. During the heating-up stage, the easily reactive part of the SL was 50.07%, and it was converted directly into oil, gas, asphaltene (AS), and preasphaltene (PA) simultaneously. There was no significant secondary hydrogenation conversion of the AS and PA products. During the isothermal stage, the hard-to-react part was predominantly converted into AS and PA, while the remaining easily reactive part continue to react completely. The conversion of AS and PA into oil and gas was a rate-controlling step during this stage. The amount of unreacted coal estimated using the model calculated in the isothermal stage was 2.98%, which was significantly consistent with the experimental value of 2.81%.

Hydrogen-donating behavior and hydrogen-shuttling mechanism of liquefaction solvents under Fe- and Ni-based catalysts

The H-donating solvent plays a crucial role in both oil yield and products distribution during direct coal liquefaction. Meanwhile, liquefaction catalyst significantly influences the H-donating behavior of the solvent and the pathways of hydrogen transfer. In view of insufficient understanding on the impact of catalysts on H-donating behavior of solvent and hydrogen transfer pathways in direct liquefaction, in this study, non-H-donating solvents including naphthalene, 1-methylnaphthalene and pyrene (Py) and H-donating solvents including tetralin (THN) and 9,10-dihydroanthracene (DHA) were chosen as the solvents. The Shenhua nano-sized Fe-based and the prepared Ni/Al2O3 catalysts were used to investigate their effect on H-donating behavior of the solvent and H-shuttling mechanism. Results show that liquefaction solvent obviously affects coal conversion and products distribution no matter Fe-based or Ni-based catalyst was used. When non-H-donating solvent is used as liquefaction solvent, coal conversion is lower than that with THN or DHA as solvent. The addition of Py to THN as solvent improves the utilization of effective hydrogen in non-catalytic liquefaction, which is ascribed to hydrogen transfer effect of Py; however, hydrogen transfer mainly occurs through direct combination of gaseous H2 with radicals generated from coal pyrolysis in presence of Fe-based catalyst, with minimal shuttle action of solvent hydrogen. On the contrary, the Ni-based catalyst aids in enhancing the hydrogen shuttle effect of the solvent, and the hydrogen transfer path primarily involves H2 to solvent and then to coal, which is ascribed to good hydrogenation ability of Ni-based catalyst. Under the action of Fe-based catalyst, DHA as liquefaction solvent exhibits lower H-donating capability compared to THN, and approximately 65% of total hydrogen consumption is effectively utilized for coal liquefaction, along with about 35% of total hydrogen consumption for the hydrogenation, ring opening, and side-chain scission reactions of DHA. However, about 96% of total hydrogen consumption is effectively utilized for coal liquefaction when THN used as solvent, indicating that THN as liquefication solvent is more conducive to the transfer of gaseous hydrogen to free radical fragments from coal pyrolysis compared to DHA.

Simulation study for identifying the mechanism of direct liquefaction of coal-related model compounds with methanol as solvent

Simulation study for identifying the mechanism of direct liquefaction of coal-related model compounds with methanol as solvent

Direct Liquefaction of South African Vitrinite- and Inertinite-Rich Coal Fines.

In this investigation, coal fines enriched with inertinite were used for direct liquefaction experiments. For comparison, a vitrinite-rich coal typically utilized in coal-to-liquid processes was also employed. To assess the impact of mineral matter content, demineralization was used to remove most of the inorganic constituents. The findings revealed that the inertinite-rich coal exhibited lower liquefaction conversions due to a reduced proportion of reactive macerals and elevated levels of inorganic mineral matter. These conversion values exhibited a strong correlation with the quantity of reactive macerals present in the parent coals. For the inertinite-rich coal, the presence of inorganic mineral matter impeded the liquefaction process but facilitated the CO2 gasification reactions of the derived chars. To evaluate their potential in gasification processes, CO2 gasification experiments were conducted and the reactivities and apparent gasification activation energies of both coal chars, liquefaction residue chars, and preasphaltene and asphaltene (PAA) chars were calculated. These calculations were carried out using the random pore model (RPM) and volumetric reaction model (VRM). The chemistry, reactivity, and kinetics of residue gasification conversion are not thoroughly understood, yet they hold significant importance in optimizing syngas production within gasification processes. The findings from this work highlight significant differences in liquefaction conversion values, product distribution, and composition. These differences are influenced by factors such as maceral composition, inorganic mineral matter content, hydrogen-donor capabilities of the solvent, and liquefaction reaction temperatures. Additionally, these variables affect the CO2 gasification reactivity of liquefaction solid residue chars.

Retracted: Experiment and Algorithm Research of Coal Direct Liquefaction Residual Oil Pyrolysis and Coking Technology Based on Lumped Kinetic Engineering

Retracted: Experiment and Algorithm Research of Coal Direct Liquefaction Residual Oil Pyrolysis and Coking Technology Based on Lumped Kinetic Engineering

Operational experience with miscanthus feedstock at the bioliq® fast pyrolysis plant

Fast pyrolysis is a thermochemical process for direct liquefaction of lignocellulosic biomass that offers flexibility in terms of feedstock variability since all biomass macromolecules are converted. In contrast to this expectation, it is also obvious that there are limits to feedstock flexibility once a fast pyrolysis plant has been built. This relates to the simple fact that any pretreatment is to a certain extent specific for one type of biomass, but also to the observation that liquid yield can vary widely depending on the feed. Different bio-oil yields directly affect heat management and volume flows in an installation. Laboratory equipment has very limited suitability to assess flexibility of a large scale implementation. To address this shortcoming, a change in feedstock with significantly different bio-oil yield was conducted in the bioliq® pilot unit that was designed for wheat straw with a feedstock capacity of 500 kg h−1. Miscanthus was used in two experimental campaigns that each lasted two weeks. While steady state operation succeeded, feedstock capacity had to be reduced significantly to around 200 kg h−1 to allow for a better control of pressure fluctuations in the hot gas section. An evaluation of volume flow rates reveals that these fluctuations are not due to an increased volatile yield. It is concluded that plugging issues caused by an increased reactivity of the produced volatiles likely caused the observations and limitations to plant capacity. The specific heat demand for the reactor of the fast pyrolysis unit was estimated to be approx. 0.83 and 0.76 MJ kg−1 for both miscanthus campaigns and ca. 0.67 MJ kg−1 for wheat straw. Heat supply to the reactor was not a limiting factor when changing the feedstock because the low feedstock rate outweighed the increase in specific heat demand. The yield distribution from miscanthus has been compared to experiments conducted in parallel in a smaller process development unit with a feedstock capacity of 10 kg h−1. The results impressively show the influence of ash content on the yield distribution and also the importance to focus on (earth) alkali metals to better describe their catalytic activity during biomass pyrolysis.

Electrification of Biorefinery Concepts for Improved Productivity—Yield, Economic and GHG Performances

Demand for biofuels will likely increase, driven by intensifying obligations to decarbonize aviation and maritime sectors. Sustainable biomass is a finite resource, and the forest harvesting level is a topic of ongoing discussions, in relation to biodiversity preservation and the short-term role of forests as carbon sinks. State-of-the-art technologies for converting lignocellulosic feedstock into transportation biofuels achieves a carbon utilization rate ranging from 25% to 50%. Mature technologies like second-generation ethanol and gasification-based processes tend to fall toward the lower end of this spectrum. This study explores how electrification can enhance the carbon efficiency of biorefinery concepts and investigates its impact on energy, economics and greenhouse gas emissions. Results show that electrification increases carbon efficiency from 28% to 123% for gasification processes, from 28% to 45% for second-generation ethanol, and from 50% to 65% for direct liquefaction processes. Biofuels are produced to a cost range 60–140 EUR/MWh-biofuel, depending on the chosen technology pathway, feedstock and electricity prices. Notably, production in electrified biorefineries proves cost-competitive when compared to pure electrofuel (E-fuels) tracks. Depending on the selected technology pathway and the extent of electrification, a reduction in GHG emissions ranging from 75% to 98% is achievable, particularly when powered by a low-carbon electricity mix.

Industrial Scale Direct Liquefaction of E. globulus Biomass

This work presents the study of Eucalyptus globulus bark and sawdust direct liquefaction. Laboratory scale experiments were carried out to assess the impact of several variables on the reaction yield and the sugar content of the bio-oil. These variables were the biomass type and concentration, the solvent, and the reaction time. The results show that E. globulus sawdust presented the highest yields (>95%), but the highest sugar content after water extraction was obtained for E. globulus bark (~5.5% vs. 1.2% for sawdust). Simultaneously, industrial-scale tests were carried out at the ENERGREEN pilot plant using the same reaction variables, which resulted in reaction yields of nearly 100%. The reagents and raw materials used, as well as the products obtained (bio-oil, reaction condensates, polyols, and sugar phases) were characterized by elemental analysis, infrared spectroscopy, thermogravimetry, and high-performance liquid chromatography with mass spectrometry. The heating value of the bio-oils is higher than the original biomass (higher heating value of E. globulus sawdust bio-oil 29 MJ/kg vs. 19.5 MJ/kg of the original E. globulus sawdust). The analyses of the bio-oils allowed us to identify the presence of high-added-value compounds, such as levulinic acid and furfural. Finally, a study of the accelerated aging of liquefied biomass showed that the biofuel density increases from 1.35 to 1.44 kg/dm3 after 7 days of storage due to the occurrence of repolymerization reactions.

Condensation of residue during direct liquefaction of a high-vitrinite coal

To understand the formation of residues and its relation with the vitrinite structure and the products yield in direct coal liquefaction (DCL), a high vitrinite low-rank coal, Naomaohu (NMH), is studied at 380–460 °C in the presence of tetrahydronaphthalene and absence of a catalyst. The structures of coal and residues are characterized by the proximate and ultimate analyses, 13C nuclear magnetic resonance, and the electron spin resonance. Beside the frequently seen coal conversion and products yield at various temperatures and time, the products yield and the residues structure parameters are correlated with the residues yield (YRes) and the quantity of hydrogen donated from tetrahydronaphthalene (QH). It is found that the DCL can be roughly defined into two regions demarcated by 420 °C, with limited condensation at 380–400 °C and intensive condensation at 440–460 °C, for example. These two-region behaviors can be clearly evidenced by the different trends in products yield and the residues parameters, such as those relevant to the cleavage of bridge bonds (fal, Cn, δ-C and δ-O) and those relevant to the residues’ condensation (far, Xb, RD and H/C), against YRes and QH. The two-region behavior is important for optimization of DCL conditions and its processing scheme.

Modified network kinetic model for coal pyrolysis with high-value products and low carbon emissions

Pyrolysis is a clean and efficient technology for the conversion of low-rank coal. Its key product is tar with high value. The complex composition of tar limits its further effective utilization. Although most kinetic models can provide the final distribution of three-phase products in coal pyrolysis, an effective prediction method for the specific composition of tar and gas has not yet been developed. Most numerical models serve to improve the total yield of volatile matter and cannot provide theoretical guidance for the improvement of tar quality or the reduction of carbon emission. Based on the basic assumptions of the CPD (Chemical Percolation Devolatilization) model for product molecules structure and generation mechanism, this paper proposed a more sophisticated method for dividing tar composition, which can achieve the division of light, medium, and heavy fractions of tar components according to boiling point. Light gas composition could be obtained with the combination of FG(Functional Group) submodel. The influence of pyrolysis final temperature, heating rate, and environmental pressure was explored for the yield and distribution of products of 18 coals. The simulation results showed that the total yield of tar was affected by both coal structure characteristics and operating parameters. Under conditions favorable for evaporation, such as low pressure and high temperature, the total yield of tar was positively correlated with the average aromatic core size in coal. Under other conditions, tar release was limited by its volatility. Coal with larger average aromatic core size corresponded to less tar yield instead. The pressure in the operating parameters had the most significant influence on the total yield of tar. The heavy fractions of tar are more sensitive to changes in operational parameters, making working conditions that increase the total yield of tar reduce tar quality. The overall carbon emission of pyrolysis is <1 kg CO2/kg tar, which is far lower than the 2–4 kg CO2/kg tar and 3–9 kg CO2/kg tar of direct and indirect liquefaction processes. Under the conditions of sufficient insulation time and no consideration of secondary reactions, the carbon emission of pyrolysis only depended on the content of carboxyl groups in the precursor functional groups. Therefore, the carbon emission intensity decreased with the increase of coal rank. For the optimization for total tar yield and tar quality, 1 atm pressure and 723–923 K temperature was optimal for low rank coals, while low temperature and heating rate with 10–20 atm pressure or high temperature and heating rate with 45–50 atm pressure were optimal for medium rank coals. For the optimization of light tar yield and tar quality, 6–9 atm pressure was optimal for low-rank coals, and 1–3 atm pressure was optimal for medium-rank coals.

Aspen Plus® Modeling and Simulation of an Industrial Biomass Direct Liquefaction Process

The current energy and climate crisis calls for immediate action in replacing fossil fuels with those derived from renewable sources. The Energreen process performs the direct liquefaction of biomass to produce a liquid biofuel for the cement industry and an aqueous solution of added-value compounds for further processing. The present work details the development of an Aspen Plus® model to simulate this biomass liquefaction process. The proposed model describes the Energreen liquefaction process using simplified reaction kinetics and thermodynamic models. The model was validated using data from a real liquefaction pilot plant with a deviation of 6.4%. The simulation, conducted with several biomass samples of variable compositions, showed that the process is robust enough to deal with different compositions and, due to the substitution of the fossil fuels presently used in the cement plant, it will allow savings of up to USD 102,000 per year to be achieved. Several analyses of the sensitivity of the results to the process variables were performed and it was possible to identify the reactor temperature and the reaction activation energy as the most impactful parameters on the process output. Overall, the results allow us to conclude that the proposed model is a solid framework for the optimization of industrial liquefaction processes.

Comparison of two-stage and single-stage liquefaction schemes for their effect on conversion and liquid yield of two low rank coals

Balancing the rates of coal radical fragments’ generation and hydrogen donation is crucial to inhibit the radical fragments’ condensation for a high oil yield and low hydrogen consumption in direct coal liquefaction (DCL). Two-stage liquefaction (TSL) has been proposed to be effective for balancing these rates under mild conditions but little work can be found in the literature on the comparison of TSL with single-stage liquefaction (SSL). This work studies direct liquefaction of two low-rank coals (NMH and SW) of very different volatile content under various TSL and SSL schemes in systems with different hydrogen donation ability. The coal conversion and products yield in different liquefaction schemes are correlated with their organic structure characterized by 13C NMR and predicted by a structure model. It is found that for the total 40 min liquefaction, the TSL scheme with 10 min at 420 ℃ followed by 30 min at 455 ℃ results in the highest liquid yield and lowest hydrogen consumption per liquid yield when the coal is very active but the hydrogen donation ability is insufficient. Otherwise, SSL at 455 ℃ is preferred. The coal conversion, liquid yield and hydrogen consumption per liquid yield of NMH under above TSL scheme at coal:THN= 1:2 are 85.5 wt%, 55.9% and 48.4 mmol-H/g-Liquid, respectively.

A hybrid kinetics model for the bond cleavage of low rank coals

The amounts (NB,t) and rates of bond cleavage of coal are essential for the development and optimization of pyrolysis and direct liquefaction processes. A hybrid first order kinetics model is developed in this work to suit the complex and diverse properties of covalent bonds in coal, and the NB,t of four low rank coals at 380–440 °C are fitted to determine the kinetics parameters. In specific, the hybrid model includes the single-temperature linear regression (STLR) and the multi-temperature nonlinear regression (MTNLR). The STLR method yields the maximum amounts of cleavable bonds NB,0 at different temperatures, which are then incorporated into the MTNLR model to yield the kinetics parameters, Ea and A. The hybrid model significantly improves the fitting accuracy in comparison with the single STLR or MTNLR model. The lnA∼Ea relations in the three models for four coals’ bond cleavage kinetics follow a similar compensation effect but differ from those for the mass change kinetics.

Construction of porous carbon for high-performance microwave absorbing: An efficient method to utilize direct liquefaction coal asphalt by-products

Construction of porous carbon for high-performance microwave absorbing: An efficient method to utilize direct liquefaction coal asphalt by-products

A kinetic model for the direct thermal liquefaction of pine wood

A kinetic model for the direct thermal liquefaction of pine wood