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Biofouling is a major operational problem in reverse osmosis (RO) processes. Numerous studies have focused on the control of biofouling using physical and chemical cleaning methods. However, irreversible biofouling, wherein a biofilm adheres firmly to an RO membrane surface, is hard to remove by physical and chemical cleaning methods. Irreversible biofouling originated from the formation of microbial biofilms, which comprised microbial cells and their self-produced extracellular polymeric substances. In this study, we tried to control irreversible biofouling by using a biofilm inhibitor in the RO process. Prior to testing, biofouling was classified into reversible and irreversible biofouling resistance, through laboratory scale RO unit operations under enhanced biofouling conditions. A tightly attached biofilm, which assumed to be caused by irreversible biofouling resistance, emerges after 30 h of laboratory scale RO operation. We have tested the inhibition of irreversible biofouling by using 4-NPO as a quorum sensing inhibitor. The microbial biofilm formation was found to be reduced 46 – 91% by 4-NPO in a concentration-dependent manner without affecting the microbial growth. In addition, irreversible biofouling on the RO membrane was reduced 36 – 67% by 4-NPO in a concentration-dependent manner. Furthermore, 4-NPO was able to decrease the irreversible biofouling resistance, instead of the reversible biofouling resistance, in laboratory scale RO units. The results of this study clearly demonstrated that 4-NPO was an effective biofilm inhibitor that could reduce the biofouling, especially, irreversible biofouling, in RO processes.

In this study, the release and formation characteristics of ultrafine particle matters (PM) during the gasification of Na-rich char are investigated. Two different pre-treatment methods, i.e., water washing and mineral loading, were employed to figure out the effects of various minerals on the deconvolution behaviors of PM, enabling the development of countermeasures. Furthermore, the mineralogical characteristics of the ash resulting from the mineral loading were also discussed. Results showed that a large amount of fine NaCl particles was generated during Na-rich char gasification. Gasification temperature and pressure essentially govern the concentration of Na and Cl species in the gas phase, which determines the quantity and morphology of PM. Specifically, the particle size of PM obtained at 1000 and 1050 °C is mainly distributed in the range of 0.2–0.4 μm. For the W-char gasified at 1100 and 1150 °C, the PM with the size between 0.6 and 1.2 μm is predominant. On the other hand, the particle size of PM decreased remarkably as the gasification pressure increased from 0.1 to 3 MPa. Additionally, due to the low carbon conversion rate of W-char during the CO2 gasification at 1100 °C, over 75% of the total PM were in the size range of 0.2–0.6 μm. The gasification of kaolin loaded W-char generated abundant spherical particles mainly present as alkali and alkaline earth metal aluminosilicates rather than NaCl particles. When it comes to adding diatomite into char, only a few spherical particles, mainly present as aluminosilicates, were detected, indicating the superior performance of diatomite on restraining PM release. The addition of diatomite into W-char could reduce ash fusion temperature, and the agglomerated coarse particles in bottom ash could capture the PM, which inhibited the release of PM to some extent. In contrast, the CaO added in char reacted with the clay and quartz that would otherwise immobilize Na, leading to the more intense release of Na- and Ca-bearing PM.

Coal seam gas has attracted global interest due to its economic feasibility, high gas storage capacity, and its capacity to cater to the world energy crisis in the long run. One of the most effective ways of extracting coal seam gas is through the hydraulic fracturing process. For the success of the hydraulic fracturing process, the proppant performance plays a key role. Poor proppant performance is a common observation in the field, and studies on shale and siltstone reservoirs show that the primary damage mechanisms associated with hydraulic fracturing is proppant crushing, proppant diagenesis, and proppant embedment. However, coal material due to its softer rock surface is more prone to proppant embedment than the rest of the degradation mechanisms. Primary factors affecting the proppant behaviour in coal seam reservoirs are: 1) the implementation of the hydraulic fracturing process – this includes the proppant concentration, size, type of fracturing fluid used, and the proppant type selected. The selection of proppants is critical in the coal seam gas extraction process, where the softer coal rock surface restricts the use of high strength proppants due to its vulnerability of embedding into the surface. 2) coal properties – elastic modulus of coal is the most important factor deciding the proppant behaviour in the extraction process. The elastic modulus is affected by mainly geological factors (i.e. confining pressure, temperature, tectonic deformation etc.) and the maturity of coal. Moreover, we highlight the changes in elastic modulus of coal that are occurred due to the coal-water and coal-methane interaction, in which the effect of moisture on coal properties is significantly higher than methane interaction, for the reason that the coal matrix tends to chemically bind well with the water molecules. However, due to the heterogeneous nature of coal and the changing of reservoir conditions, we infer that influential factors must be re-evaluated for targeted seams, and thereby develop a suitable proppant implementation process.

The main aim of this work was to study the effect of pH on lactate- and acetate-based bioH2 production from the dark co-fermentation of 80% tequila vinasse and 20% nixtamalization wastewater (w/w) by mixed culture. A 3-L well-mixed batch reactor was operated at constant pH values of 5.8 and 6.5, with an accuracy of ±0.05 pH units in all the cases. Regardless of pH, bioH2 production derived mostly from the consumption of lactate. No significant differences were observed in the amount of bioH2 produced, i.e. 2133 NmL/Lreactor with a maximum rate of 155 NmL/L-h. Compared to a pH of 5.8, pH 6.5 shortened the lag time but promoted bioH2 sink through propionate formation. Based on the above results, a two-stage controlled-pH strategy was proposed by maintaining the first stage at pH 6.5 and the second stage at pH 5.8 for avoiding long fermentation time and propionogenesis, respectively. The pH-shift strategy reduced the operational time and enhanced bioH2 production by 17%. Besides, this strategy also stimulated the syntrophy between Clostridium and Lactobacillus, and reduced the proliferation of Blautia and Propionibacterium, trending bioH2 production to enhanced efficiency. Overall, microbial dynamics showed that successful bioH2 production from lactate and acetate relies on having an optimum microbial equilibrium between producers and consumers of lactate and acetate, which was found to be pH-dependent.

In this study, we evaluated leaf extract of Thuja oreantalis L. as a natural antioxidant additive for biodiesel oxidation stability enhancement. Primarily the total phenolic content has been tested by Folin ciocalteu method and free radical scavenging capacity has been tested against DPPH (1,1-diphenyl-2-picryl-hydracyl). Other techniques like HPLC, FT-IR and 1H NMR analyses have been done for identification of the antioxidant compounds. The Thuja extract is further characterized by powder XRD, SEM, TEM and BET techniques. A total of six concentrations of Thuja extract (TSE) are used for evaluating the antioxidant activity in biodiesel i.e. 0 ppm (TSE0), 100 ppm (TSE1), 250 pmm (TSE2), 500 ppm (TSE3), 1000 ppm (TSE4) and 2000 ppm (TSE5). The results revealed that a minimum concentration of 100 ppm of Thuja extract in the WCB produced from waste cooking oil was capable of enhancing its induction period (IP) from 4.55 h to 6.79 h, which meet both the standard specifications for biodiesel oxidation stability i.e. European (ENE14214) and American (ASTM D-6751). Comparison of oxidation stability enhancement in biodiesel employing TBHQ (tertiary butylhydroquinone) and Thuja extract has been studied along with long storage periods. This study adds one more dimension in the field of exploration of natural antioxidants for biodiesel quality enhancement.

Hydrogen (H2) produced from fossil sources via steam reforming of natural gas requires further purification before it can be safely used for human consumption and as fuel to generate electricity from hydrogen fuel cells. A promising technology for H2 purification from carbon dioxide (CO2) is by pressure swing adsorption (PSA) using palm kernel shell activated carbon. The adsorbent exhibited higher affinity for CO2 than H2. The adsorption system was capable of achieving H2 purity of almost 100% with H2 recovery of 88.43%. H2 contributed 6.62 J.min−1 of the energy requirement from the total energy of 6.63 J.min−1 as a result of pressurization of the gas at 3 bar. H2 contributed 5.85 J.min−1 energy from depressurization of the gas to 1.5 bar. The modest energy requirement with high level of H2 purity and recovery demonstrated the effectiveness of PSA with pressure equalization mode for H2 purification from syngas.

The aims of this study is to investigate the effects of functional groups like C C and C OH on variation of higher heating values (HHV) of organic compounds. HHV of fuel hydrocarbons, gaseous and liquids including single bonded and multiple bonded carbons and green tea polyphenols (GTP) were determined by using Bomb Calorimeter. It was observed that, multiple bonded carbon and oxygen bonded carbon i.e. C C and C O result in less carbon reduced state while, also increase endothermicity of reactants by changing hybridization state with more s-character and hence, contribute to lower level of HHV. Besides, hydrogen bonding was also considered as the major cause of the difference in HHV of fuel hydrocarbons having the same molecular formula but different oxygen-bearing functional groups due to structure stabilization. These statements were further supported by the combination of Fourier transform infra-red spectra (FTIR) and HHV calculation of raw GTP (set as a representative of biomass) and its solid products obtained at 250 °C and 350 °C by thermal treatment done by using high temperature tube furnace.

Research reported in this publication was supported by Saudi Electric Company (SEC) and by competitive research funding from King Abdullah University of Science and Technology (KAUST). The authors acknowledge support from the Clean Combustion Research Center under the Future Fuels research program. This research used resources of the Core Labs of King Abdullah University of Science and Technology (KAUST). We also thank Eshan Singh for his help in experimental measurement of density and kinematic viscosity.

The metallurgical coke sample collected from the lower section of cohesive zone was examined by SEM/EDS. It was observed that the outer layer of coke was covered with slag and iron, and the solid solution of Ti(C,N) and V(C,N) was distributed around the slag-iron interface and iron droplets. The composition of the slag was unevenly distributed, mainly the crystalline phases of gehlenite or anorthite. The macroscopic coke pores near the slag-iron layer were filled with a large number of slag, and the interconnected pores generated by severe coke gasification reaction provide effective channels for the liquid slag to flow into the coke. The Fe-rich phase, the Ca-rich phase, and the alkalis element were also observed in the coke. Meanwhile, the octahedral spinel crystals were found in the coke pores, and the stress generated by the growth of spinel crystals may cause the formation of cracks in cohesive zone coke.

Coke combustion makes the temperature of heavy oil higher to achieve lower viscosity during in-situ combustion process. The conversion of heavy oil components into coke is significant for the start-up of combustion, but most of the current research results come from laboratory experiments. To further study the conversion of crude oil components in oilfield pilot, this paper divides the reactions of heavy oil into oxidation reaction and thermal reaction, and the reaction mechanism and characteristics are analyzed deeply. Then, the oxidation stages of different sections are determined by analyzing the data of coring wells in the oilfield. Furthermore, the infrared spectra and GC-MS of crude oil in different oxidation stages are analyzed to observe the changes of components and functional groups of heavy oil in this process. Combined core analysis results and the reaction mechanism of heavy oil, the conversional sequence of different components is obtained, and then a systematic heavy oil component conversion path is formed. The above studies validate and improve the conclusions of laboratory experiments and deepen the understanding of the conversion of heavy oil components and the formation of fuel in fire flooding process.

Temperature and pressure are key factors affecting gas–liquid two-phase flows in porous media. Although evidence supports the effect of temperature on coal-bed methane (CBM) exploration, the fluid production is, at present, not sufficiently understood. By conducting nitrogen and water two-phase displacement experiments under different temperatures and pressures and monitoring the production of fluids at different times, this study obtained quantitative experimental measures for investigating the multi-phase seepage properties. The results indicated that (1) in the temperature range of 30–180 °C, the liquid produced was mainly the free water in the coal, and heating a coal reservoir facilitated the desorption of the water; (2) experimental testing provided a novel characteristic curve for the entire two-phase displacement process, which could be separated into the liquid seepage stage, gas–liquid multi-phase seepage stage, and gas flow stage; (3) increasing the temperature affected the gas and liquid phase velocities, production, and saturations during displacement; (4) with an increase in pressure, the irreducible water increased, whereas the two-phase percolation area decreased. The experimental methodology and obtained results provided evidence that during heat injection enhanced CBM recovery, the gas production rate might increase after breakthrough, with a simultaneous increase in the liquid production. Heating coal seams can thus improve the gas production efficiency, but has disadvantages compared to the initial drainage.

Nitrogen has emerged as a suitable alternative to carbon dioxide for injection into hydrocarbon reservoirs worldwide to enhance the recovery of subsurface energy. Nitrogen typically costs less than CO2 and natural gas, and has the added benefit of being widely available and non-corrosive. However, the underlying mechanisms of recovery following N2 injection into fractured reservoirs that make up a large portion of the world’s oil and gas reserves are not well understood. Here we present the laboratory results of N2 injection into carbonate rocks acquired from a newly developed oil reservoir in Iran with a huge N2-containing natural gas reservoir nearby. We investigate the effectiveness of N2 injection for enhanced oil recovery in immiscible conditions before and after gas breakthrough under a low and high differential pressures across the core. In addition to the effects of pressure, we further illuminate the impacts of fractures—induced on the cores—to assess the displacement behavior and oil recovery factor. Our findings show that an ultimate oil recovery factor of more than 40% can be achieved by N2 injection in non-fractured cores even at immiscible conditions. The ultimate recovery and the onset times for oil production and gas breakthrough are found to be lowered by increasing differential pressures as well as inducing fractures (e.g., 17% reduction in ultimate recovery due to fracturing). However, at a given time when gas-oil interface has not yet reached the production zone (outlet), both increasing differential pressures and fractures transiently enhance the recovery efficiency. As a result, the impact of fractures is more pronounced in lower differential pressures, while the impact of differential pressures is stronger in the absence of fractures. Interestingly, our results attest to the role of molecular diffusion across fracture-matrix interface as the main recovery mechanism in fractured media, which controls the system dynamics before and after breakthroughs. The results not only provide a new perspective into how differential pressures and fractures fundamentally control the effectiveness of N2 flooding but also further show the promising prospects of N2 injection for EOR even at immiscible conditions.

The behavior of the slag layer is very important for the safe and efficient operation of the cyclone barrel of cyclone-fired boiler. Ash parameters are the key factors affecting the formation and evolution of the slag layer. In order to figure out whether a stable slag layer could be formed when the cyclone-fired boiler burns the coal with low ash content or burns the coal with high ash melting point mixed with various contents of fluxing agent, the effects of ash content and fluxing agent on slag layer behavior are numerically examined for a vertical cyclone barrel. The decrease in the ash content can significantly reduce the mass flux of the captured particles as well as the velocity of the liquid slag layer. However, a stable slag layer can still be formed on the internal surface of the cyclone barrel even when the coal with a low ash content of 6.77% is burned. When the mass ratio of the fluxing agent is increased, the area of the internal surface covered with slag layer expands, whereas the solid slag layer becomes thinner. The amount of the fluxing agent has an optimal value. For the studied coal, when the mass ratio of the fluxing agent is 2.8%, the area of the internal surface covered with the slag layer expanded by about 37%, compared with the case without fluxing agent.

The Ni/SBA-15 and Ni/TiO2 catalysts with 20 wt% nickel with different metal–support interaction strength were designed using ordered mesoporous silica (SBA-15) and TiO2 (P25). The Ni/SBA-15 and Ni/TiO2 catalysts with 20 wt% nickel were investigated using various characterization techniques. It was found that the Ni/SBA-15 and Ni/TiO2 catalysts with 20 wt% nickel possess different nickel particle size and different reducibility because of the different strength between nickel and support interaction. Both Ni/SBA-15 and Ni/TiO2 catalysts were tested for the hydrodeoxygenation reaction of a model bio-oil using a fixed-bed reactor at different evaluation conditions. It was found that under high hydrogen pressure (≥7 bar), both Ni/SBA-15 and Ni/TiO2 catalysts are highly efficient because the organic oxygen compound could be converted completely. And the product selectivity is very sensitive to the hydrogen pressure. Under low hydrogen pressure (3–5 bar) Ni/TiO2 catalyst show rather higher selectivity toward aromatic hydrocarbon as compared with Ni/SBA-15 catalyst. Lower hydrogen pressure and reaction temperature will be beneficial to the aromatic hydrocarbon production. It is very important to reduction for the H2 consumption cost. TiO2 is a very potential candidate support for the catalyst design aiming to the sustainable aromatic hydrocarbon production.

To study the gas injection scenario for successful implementation of enhanced oil recovery (EOR) processes, the prediction of interfacial tension (IFT) between injected gas and the crude oil is of paramount significance. In the present study, some intelligent methods were developed for determining IFT values between supercritical CO2 and normal alkanes. IFT was considered as a function of temperature, pressure, and molecular weight of normal alkanes. The developed methods were Multilayer perceptron (MLP), Genetic Algorithm Radial Basis Function (GA-RBF), and Conjugate Hybrid-PSO ANFIS (CHPSO-ANFIS). The average absolute percent relative errors (AAREs) for the stated techniques were found to be 2.59%, 1.39%, and 1.81%, respectively, showing that GA-RBF is the most efficient technique. This model was then compared to the other previously developed models in literature. It was also found that the current GA-RBF model with AARE of 1.39% surpasses the previously developed models. Finally, the results of the Leverage approach showed that GA-RBF model could be trusted to predict the IFT of the normal alkane- supercritical CO2 systems in the used range of pressure, temperature, and n-alkanes. This study represents the most reliable technique in predicting the IFT value between supercritical CO2 and normal alkanes to be applied in studies on gas injection processes.

Permeability is an important parameter that helps understand the gas mass transport behavior in tight porous media. However, measuring the permeability of tight porous media accurately is an arduous task. Gas flow differs from liquid flow in regards to high compressibility, slippage effect, and sometimes adsorption. Slippage effect can be significant when the pressure is low or the pore diameter is small. Increasing pressure eliminates the slippage effect; however, high pressure is not always achievable under lab or field production conditions. The measurement of permeability during gas flow in a porous media is also greatly affected by the adsorption-induced surface diffusion process. In this study, a combined experimental–mathematical method for determining the permeability of tight porous media was developed. Steady-state measurements were conducted to obtain methane flux under different pressures for shale and tight reservoirs. The apparent permeability and permeability without slippage were calculated. Using the measured parameters, a mathematical model was derived to determine the intrinsic permeability, and the viability was tested with experimental results. This work provides an alternative approach to estimate the permeability of tight porous media during the gas mass transport process by considering both the slippage effect and gas surface adsorption. Parameters in the model can be easily measured through experiments for low pressures. Experimental verification shows that the error of permeability estimation can be decreased by approximately 10%.

Transformation of pore and fracture structure of coals with supercritical CO2 (scCO2) –H2O is a key to CO2 injection and CH4 production efficiencies during the CO2 enhanced coalbed methane process. To study the transformation of pores and fractures in the coals with CO2, two reservoir conditions, which simulate1000m (45 °C, 10 MPa) and 2000 m (80 °C, 20 MPa) depths, are applied to four types of high metamorphic coals from Qinshui Basin to study the influences of temperature and pressure on pore volume and pore sized distribution change. Nuclear magnetic resonance, high pressure mercury intrusion, X-ray CT scanning and permeability experiments are performed and the effects of scCO2 on coal permeability and the influencing factors are discussed. The results show that scCO2-H2O has a positive effect on the improvement on the pore fracture system. It could add or expand pores and fractures, leading to the increase in pore number, porosity, pore volume, pore specific surface area, connected pore volume, and pore throat number. And then, increased the permeability which had a positive correlation with the experimental temperature and pressure. The growth of permeability could be as high as 114.10 times, and it was higher in horizontal to bedding direction than that of the vertical to bedding direction. Coal expansion could lead to the addition and enlargement of micro-fractures and enhance the connectivity between seepage pores and fractures. Mineral dissolution could lead to the formation of a large number of effectively connected and non-effectively connected pores, especially the latter, which was positively correlated with simulated temperature and pressure. In addition, the effectively connected pores tend to develop in vertical original micro-fractures. Moreover, the more complete the reaction is, the more favorable it is to increase the pore volume of fractures.

Gasification of biomass in bubbling fluidized beds can be limited by accumulation of unconverted char particles during the process. The amount of unconverted biomass depends on the residence time of the fuel particles. This study demonstrates a method for measuring the biomass residence time over the conversion period at a given air flowrate and a given amount of biomass in a bubbling bed using the variation of bed temperature and fluid pressure recorded over time. The results show that biomass conversion is characterized by the devolatilization and extinction times. The two biomass residence times increase with decreasing air flowrate and increasing amount of biomass charged in the bed. The amount of unconverted char between the two characteristic times also increases with decreasing air flowrate and increasing biomass load. The total heat loss during the devolatilization is observed to increase with increasing air flowrate and amount of biomass in the bed. Correlations are proposed for predicting the mean biomass residence time, the amount of unconverted char particles and the devolatilization heat loss at a given operating condition. The results of this study can be used in determining the bubbling bed properties and solid circulation rate required to decongest the accumulated char particles in the bed.

Organic matter in Baiyinhua lignite (BL) was characterized by direct characterizations with solid-state 13C nuclear magnetic resonance spectrometer and X-ray photoelectron spectrometer, thermal approaches with thermogravimetric analyzer, Curie-point pyrolyzer-gas chromatograph/mass spectrometer, and sequential thermal dissolution (TD) followed by the analysis with a gas chromatograph/mass spectrometer. The results show that normal alkanes, alkylnaphthalenes, and oxygen-containing organic compounds with Ar–O– and –(C O)–O– moieties are predominant in BL. Aliphatic carbon atoms are dominated by methylene with the average carbon number of 2. The number of aromatic rings (ARs) and substituents attached on the ARs are 2 and 4, respectively. The most abundant organic oxygen species contain Ar–O– moieties. The cleavage of >Cal-Cal Car-Cal Car–O– bonds is the main reaction during the pyrolysis at 500 °C, which plays the most important role in devolatilizing organic species from BL. The products from the TD differ greatly due to the distinct pathways. When using methanol as the solvent, >C–O–C O)–O– is negligible, which is the main reaction of TD in ethanol.

Biodiesel is known as a prominent candidate for the replacement of fossil-based fuels since the sources of these fuels have been depleted in the past few years. The most convenient process to produce biodiesel is the transesterification of triglycerides with an alcohol in the presence of a suitable catalyst. At the end of the reaction, two liquid phases comprised of biodiesel (main product), glycerol (by-product) and unreacted alcohol are co-exist. Phase equilibrium study is a tool to design the equipment that involved in the biodiesel production and purification processes. In this work, biodiesel was produced through the transesterification of linseed oil with methanol. Afterwards, the liquid–liquid equilibrium (LLE) data were measured for the ternary systems containing linseed oil biodiesel, methanol and glycerol at three different temperatures and atmospheric pressure. The binodal curves were determined by the cloud-point method in isothermal conditions. The adequacy of the experimental tie-lines has been confirmed using the Othmer–Tobias correlation. The results have been correlated using NRTL and UNIQUAC models. The binary interaction parameters of system components have been adjusted via an evolutionary algorithm so-called “BSOA” without and with closure equation. To predict the equilibrium composition, UNIFAC, UNIFAC-LLE, UNIFAC-DMD and UNIFAC-LBY models were used. Average deviations between the calculated and experimental data for NRTL, UNIQUAC, UNIFAC, UNIFAC-LLE, UNIFAC-DMD and UNIFAC-LBY were 1.574%, 1.380%, 3.187%, 3.164%, 3.881% and 3.960% respectively which show that UNIQUAC model represents the best correlation of experimental tie-lines. RMSD values have been improved by implementation of the closure equation.

The water contained in lignite generally exists in various forms and the energy required to remove them from coal is also different. Thus, two different rank lignites with different water contents from Yunnan and Inner Mongolia provinces in China were selected for analyses of water forms and dewatering energy consumption. The forms of water contained in these two lignites were classified using differential scanning calorimetry (DSC). The results show that the water in the lignite mainly contains freezable water and non-freezable water, and further the freezable water can be divided into free water and freezable bound water. The water above 40% moisture content of dry coal weight in coal sample is free water; that between 27% and 40% of dry coal weight is freezable bound water; and that less than 27% of dry coal weight is non-freezable water, which is nearly independent of coal rank. Then, the microwave drying and the fixed bed drying devices were employed to dry these two lignites, and the dewatering energy consumption during drying processes were measured and calculated to compare the change of energy consumption for removing different types of water. The results show that 500–600 W microwave field is suitable for drying lignite because the water is difficult to be completely removed under 450 W and slight pyrolysis is prone to occur for lignite when the microwave power is higher than 700 W. The dewatering energy consumption of total moisture in microwave field under 500–600 W is 8.6–15.3 kJ/g H2O, and those of freezable water and non-freezable water are 8.7–12.5 kJ/g H2O and 8.5–21.8 kJ/g H2O respectively. In addition, the dewatering energy consumption of 50 g lignite in fixed bed drying at 120–160 °C is 1.3–3.6 kJ/g H2O. In order to take advantages of microwave and fixed bed, these two methods are coupled to dry lignite for reducing energy consumption and improving drying efficiency. For the best compromise between drying energy and drying time, it is recommended to use 600 W power microwave field to remove free water in lignite, and then to use the fixed bed to remove the remaining water at 160 °C. The water re-adsorption amount of the upgraded coal is about 1/3 lower than that of raw coal.

The combustion characteristics of particle group are different from the combustion of a single particle, owing to the physicochemical effect and interaction among particles. The current work investigated the effect of the increasing particle concentration on the group combustion with the consideration of temperature and solid fuel type, including bituminous coal char and petroleum coke. A visual imaging technology was used to record and analyze the combustion process and group evolution of burning particles in the two-dimensional scale. Results showed that a delayed combustion phenomenon was found for both coal char and petroleum coke with the increasing particle concentration in a group. The burnout time increased in multiples from the combustion of a single particle, dispersed particles to a particle group. The total carbon conversion and combustion rate of the particle group significantly decreased with the increasing particle concentration in the group, especially for the bituminous char of a high reactivity. With increasing the combustion temperature, the burnout time was additionally prolonged from 20% to 80% between the internal and external particles in the particle group. The theoretical analysis with the consideration of Stefan flow, gas diffusion, and gas-solid reaction was used to propose the delayed combustion mechanism, and the results matched well with the experimental data. The increasing particle concentration in the group, which consumed the oxygen, generated the advance effect of Stefan flow, and hindered the oxygen diffusion, was the key factor to delay the group combustion. For the group combustion of petroleum coke with low reactivity, although the surface reaction was the controlling step, the reactant gas diffusion inside the group could not be ignored. For the group combustion of coal char particle with high reactivity, the diffusion of the reactant gas in the group was the dominant controlling step for the delayed combustion behavior.

GCI combustion mode has become an interesting topic for high thermal efficiency and low emissions, while ignition problem and knocking combustion limited its application. The blending fuel of gasoline/Hydrogenated Catalytic Biodiesel (HCB) can extend the working conditions for GCI engines because there is no mixed and ignited problem. In this paper, the spray liquid length, ignition delay and flame lift-off length of three gasoline/HCB blends with different blending ratio are measured simultaneously in a constant volume combustion chamber for providing enough data to guide the gasoline/HCB blends used in GCI combustion mode. The experimental results show that the ignition delay and lift-off length decrease with increasing the proportion of HCB in blends, while the spray liquid length shows an opposite trend. Moreover, for gasoline/HCB blends, chemical ignition delay plays a leading role in the total ignition delay and the cycle-to-cycle variation will be decreased with increasing the blending ratio of HCB. On the other hand, the spray and combustion characteristics of G70H30 and G50H50 are compared with those of diesel for further applying the blended fuel in compression ignition engines. The natural luminosity intensity of diesel is higher than that of G50H50 and G70H30 even the injection pressure of diesel is higher than that of blending fuel, which means the blending fuels have relatively lower soot emission. Meanwhile, the ignition delay and flame lift-off length of G50H50 are getting close to the diesel results. Moreover, there is a big difference in ignition delay for these three fuels under low oxygen concentration, while the difference decreases with increasing the oxygen concentration.

Microwave (MW) heating offers numerous advantages over conventional heating. Its characteristics of fast internal heating, volumetric heating, and low energy consumption enable microwave torrefaction (MWT) of biomass to be performed. The purpose of this article is to review the current state of MWT of biomass. A brief explanation of MWT, including experimental setups and the effects of several important parameters, are reviewed and discussed. Potential future directions and challenges regarding MWT are also discussed. It is known that the MW power level, types of MW absorbers (catalyst), and particle size can significantly influence the performance of torrefied biomass in terms of energy and mass yields, mass loss, H/C and O/C ratios, fuel ratio, and high heating value. The effect of operating condition on products derived from MWT needs to be further investigated in order to make the technology feasible and reliable. Overall, MWT has the potential to serve as energy-efficient method to improve the performance of biomass.

Considering drawbacks such as the low inhibition efficiency and short inhibition life of an existing pure hydrogel, a new physicochemical composite hydrogel inhibitor was developed. First, tea polyphenol radicals were grafted and polymerized onto a hydrogel and then mixed with HNTs (halloysite nanotubes). Electron microscopy, Fourier transform infrared spectrometry and thermal gravimetric analysis were used to analyze the inhibiting effect and mechanism of the composite hydrogel inhibitor. Research shows that (i) the graft copolymerization of tea polyphenols with acrylate will increase the contact area between the grafted gels and the surroundings, thus improving the water absorption capability of the hydrogel; (ii) the added tea polyphenols reduce the content of hydroxyl in coal and the content of carboxyl and carbonyl generated during the oxidation of aliphatic groups and it also increase the content of stable ether bond; and (iii) by absorbing the combustible gases and producing water, HNTs can shorten the exothermic temperature range (From 120.22 ℃ to 572.22 ℃) of coal sample processed by composite hydrogel, and it can reduce the release of heat, which is 2536.73 J/mg. These results suggest that the composite hydrogel can distinctly inhibit the spontaneous combustion and oxidation of coal, achieving stable inhibition in many aspects such as its physics, chemistry and thermal stability during the whole process of spontaneous combustion.

As an oxygenated additive, 2, 5-dimethylfuran (DMF) addition is a method to reduce effectively the diesel particulate matter (PM) emissions. However, the influences of DMF addition on oxidation behavior and nanostructure of PM produced from diesel engines are not well understood. This study explores the effects of DMF addition on morphology, nanostructure and oxidation reactivity of diesel exhaust particles. Experiments were conducted in a high pressure common-rail diesel engine fueled with pure diesel, DMF10 (90% diesel and 10% DMF, by vol.), DMF20 (80% diesel and 20% DMF, by vol.), under two different engine loads at the same engine speed (1800 r/min). Particulate samples were collected from engine exhaust tailpipe and further characterized by transmission electron microscope (TEM), Raman spectroscopy (RS) and thermogravimetric analysis (TGA). Results showed that the physicochemical features of diesel exhaust particles can be influenced by both engine load and DMF blending ratio. Under the given engine load condition, soot particle from DMF20 was more reactive to oxidation, followed by samples from DMF10 and diesel. With a rise of DMF blending ratio, both primary particle diameter and fringe length decreased while fringe tortuosity increased. Similar with the results obtained by TEM, the larger D1-FWHM and ID1/IG for blended fuels demonstrated less graphitic structure. Specially, the fringe separation distance and AD1/AG did not show statistically significant differences between various tested fuels in this study. The more disordered structures explained the higher reactivity of soot from blended fuels. Independently of tested fuel, soot particles exhibited larger primary particle diameter and more graphitic structure under higher engine loads, indicating a lower soot oxidation reactivity.

Spark assistance is an effective method to improve combustion stability of homogeneous charge compression ignition (HCCI) with lean mixture. Ethanol, a renewable energy, blended with commercial fuels is a promising method to deal with problems of energy safety and greenhouse gas (GHG) emission. However, the influence of ethanol blends on spark ignition to compression ignition is not clear. To this end, this study presents experimentally fundamental investigation on the compression ignition (with and without spark assistance) of ethanol-blended gasoline surrogate fuel in an optical rapid compression machine at the equivalence ratio of 0.5. Three fuels with different octane sensitivities (S) comprising n-heptane/iso-octane/ethanol were formulated and S is the difference between research octane number (RON) and motor octane number (MON). Effective temperature of experiments ranges from 730 K to 860 K, overlapping most of the temperature region with negative temperature coefficient (NTC) of iso-octane at the corresponding equivalence ratio, and the pressure is consistence with engine-relevant operating conditions. The results show that more fuel reactivity of ethanol than iso-octane at 860 K is not attributed to the NTC behavior of iso-octane but to the reactive species generation in ethanol oxidation. There is always a positive correlation between effective pressure and knock intensity (KI). At lower temperature (

At the near-limit conditions, the behavior of detonation propagation manifests unstable modes; those modes are classified into three types, i.e., steady mode, fluctuation mode and fast failure mode. This work aims to elucidate essential physical relation between those unstable propagation modes and the instability of detonation. The velocity of the combustion wave in five mixtures (i.e., C2H4-6N2O, CH4-2O2, 2H2-O2, 70% and 85% Ar diluted C2H2-2.5O2) are experimentally measured to analyze velocity behavior near the limits. The stability parameter χ is computed from CHEMKIN package and chemical kinetics. According the detonation cellular pattern and the calculation of χ, C2H4-6N2O and CH4-2O2 are considered as unstable mixtures (with highly irregular cells), 2H2-O2 is characterized as stable mixture (with regular structure), 70% and 85% Ar diluted C2H2-2.5O2 are determined to be highly stable mixtures (with highly regular pattern). In the above unstable/stable/highly stable mixtures, the detonation propagation behavior at the near-limit condition presents Slow Decay/ Fluctuation/ Fast Failure modes. Evidences confirm that instability (or cell regularity) dominates the propagation modes as detonation approaches the limits. The competition mechanism between detonation instability and boundary effect resulting in the slow decay of propagation velocity as the condition is outside the limits. However, for stable mixtures, due to the instability has very limited effect on the propagation of detonation, this competition mechanism is lacking, and resulting in detonation rapidly attenuates to a fast flame. In addition, the neutral stability curve (Ng et al., Combust Theor Model 2005;9:385-401) is an appropriate separatrix between Fast Failure/Fluctuation modes, a new second stability curve is proposed in this work, which is the boundary of Fluctuation/Slow Decay modes.

The microstructure of asphalt binders is believed to have a significant impact on the performance of binders used in roadway constructions. However, there are only limited studies of their nanoscale to microscale structures. Here, small angle neutron scattering (SANS) is used to study the nanoscale structure of neat asphalt binder, styrene-butadienestyrene (SBS) block copolymers and SBS modified asphalt binder. The SANS pattern for asphalt binder demonstrates that it exhibits a colloidal structure comprised of asphaltenes surrounded by resins dispersed in saturates and aromatics. Fractal-core-shell model fits to these patterns indicate that the asphaltene core size decreases with increasing temperature. Both SANS and rheology confirm that SBS modified asphalt has a thermo-reversible phase transition around 110 °C, where the SBS micelles swell and lose scattering contrast above this temperature. The thermo-reversibility of this phenomenon indicates that the mechanism of SBS modification is mostly a physical modification of the nanoscale structure as proposed in the colloidal model of asphalt. Modeling of the SANS patterns shows that neat SBS and SBS dispersed in asphalt binder have a lamellar structure surrounded by a shell. These results are useful for understanding the relationship between the nanoscale structure of asphalt binder and pavement performance, as well as potentially developing new types of modified asphalt binders.

Fossil fuels have traditionally been used in power generation systems and represent the main source of greenhouse gas emissions from this sector. Renewable fuels, especially biomass, are now being substituted for fossil fuels to reduce CO2 emissions. Co-firing biomass with coal, which has been widely practised in the UK and Europe, is one route to reduce the environmental impact of using coal. However, the deposition of ash particles and vapour species on heat exchanger surfaces during operation is a serious issue in pulverised coal and biomass fired power plant as this reduces the plant thermal efficiency and can cause fireside corrosion, which limits component lives. Deposit formation is difficult to predict as it varies with many factors including: boiler geometry, combustion conditions and fuel composition. Computational Fluid Dynamics (i.e. CFD) is one of the best modelling tools to study the flow behaviour of gases and particles around heat exchanger tubes and predict deposition. This work used an Eulerian-Lagrangian model to describe the gas flow field around tubes and the solid ash particle trajectories respectively. User Defined Functions (i.e. UDFs) were developed for the CFD package to enable the prediction of deposit growth, deposit shape and temperature gradients around superheater/reheater tubes. Deposit build up insulates such tubes from the flow of the hot combusted gas stream and reduces heat transfer between this gas stream and the steam coolant following within the tubes, thus raising the deposit temperature. The CFD-based predictions generated were consistent with available literature data. The CFD deposition model has been applied to predict deposition on air cooled ceramic probes in a 100 kWth pilot-scale, pulverized fuel (PF) combustor and compared to deposition data measured after the combustor rig runs. For modelling purposes, the geometry was simplified to a two-dimensional domain with inert spherical ash particles dispersed in air and injected at an inlet plane. Experimental data from a series of rig runs have been used to test this CFD deposition modelling approach.

Despite the several advantages compared to conventional diesel fuel, the biodiesel has poor cold flow properties, limitng its use as a fuel in moderate and cold climates. Considering that the fatty esters profile and the alcohol used affect the biodiesel physico-chemical behavior, this work explored the crystallization/melting profiles of ethyl biodiesel from different oil sources as well as of binary blends among them to improve their cold flow properties. Therefore, model ethyl biodiesels from soybean oil, beef tallow, palm oil, their fractions, olein and stearin, palm kernel, macauba, and macauba kernel oils were formulated by pure ethyl esters, their melting/crystallization temperature, cloud point, pour point, cold filter plugging point and the fraction of crystallized esters analysed. For all cases, blends decreased the cold flow properties of the heavier biodiesel. Soybean oil and tallow biodiesels, economically relevant sources, presented a CFPP of −4.28 °C and 17.12 °C, respectively, whilst some alternative sources, such as macauba and palm kernels biodiesels, presented values lower than −15 °C, which is more advantageous in cold climates. Tallow biodiesel was the only not in accordance with Regulation Agencies considering cold climates. Macauba and palm kernel oils were especially interesting to decrease the melting/crystallization temperatures of heavier biodiesels, including those from tallow beef. The best blend was those formulated with soybean and macauba kernel oils with a CFPP lower than −20 °C. This work suggested that not only biodiesels mainly composed by unsaturated esters but also by short-saturated esters could significantly improve the cold flow properties of high saturated biodiesel, being a low-cost and feasible alterative.

NO and CO are recognized as the major source of air pollution and are expected toward selective catalytic oxidation under different environments. Based on density functional theory (DFT) calculations, the formation configuration and surface activity of metal Co and nonmetal N atoms co-doping graphene (Co-N3-graphene) as substrate are investigated. Firstly, the adsorption behaviors of gas reactants on Co-N3-graphene sheet are comparably analyzed. It is found that the coadsorption of OH/NO and OH/CO molecules have the larger adsorption energies than that of the single NO or CO, thus the Langmuir-Hinshelwood (LH) mechanism for NO or CO oxidation reactions will be considered. Secondly, the coadsorption of 2NO molecules is more stable than that of the 2CO and the interaction between 2NO and 2CO molecules through Eley-Rideal (ER) mechanism are also investigated. So, the possible reaction mechanisms for NO or CO oxidation on Co-N3-graphene are explored. In the O environments, the formation of HONO or HOCO complex and NO or CO are easily generated NO2 or CO2 with smaller energy barriers (

In order to develop an efficient amphiphilic catalyst for the oxidative desulfurization (ODS) of fuel oils by H2O2, seven surfactant-like heteropoly acid catalysts were prepared, and their ODS performance was studied at varying conditions for model oils. The results indicate that phosphotungstate (PWO) has higher catalysis than phosphomolybdate (PMoO), and cetyl-methyl-imidazolium phosphotungstate ([C16MIM]3PWO) is one of the best catalysts for the oxidation of dibenzothiophene (DBT) with mere H2O2 without any other additives or extractants. The ideal amphiphilic catalysts should have at least one long alkyl group (C12–C18) in the monovalent cations so as to make them hydrophobic and oil dispersible, forming metastable W/O emulsion in oil even in the presence of excessive water. DBT can be oxidized completely within 40 min under optimal conditions (10 g model oil, 0.1 g catalyst, n(H2O2)/n(S) = 4, 313 K). [C16MIM]3PWO shows excellent reusability with little activity decline after five recycled uses, and is effective for real diesel.

Nowadays, coalbed methane recovery faces challenges such as high gas content, micro-porosity and low permeability. An exploratory study on improving coal porosity by acetone treatment was carried out. Pore size distribution and fracture development before and after acetone treatment were evaluated using a suite of integrated diagnostic techniques including rock acoustical test, weight analysis, Scanning Electron Microscope (SEM), Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared Spectroscopy (FT-IR) and mercury intrusion porosimetry (MIP). After acetone treatment, micropores are partially converted into mesopores and macropores. The porosity of coal increases by 2.66% after acetone treatment. Functional groups including hydroxy, methylene, oxygen functional groups and aromatic hydrocarbons reduce significantly and the removal of these hydrophilic groups significantly weakens the hydrophilicity of coal. New fractures appeared within 32.89% of the eroded zone, even large through-going fractures may appear after acetone treatment. The results indicate that acetone treatment is effective in improving gas productivity thus has the potential to become a new coalbed methane reservoir stimulation technology.

Diffusion coefficient is one of the key parameters determining the coalbed methane (CBM) reservoir economic viability for exploitation. Diffusion coefficient of coal matrix controls the long-term late production performance for CBM wells as it determines the gas transport effectiveness from matrix to fracture/cleat system. Pore structure directly relates to the gas adsorption and diffusion behaviors, where micropore provides the most abundant adsorption sites and meso- and macro-pore serve as gas diffusive pathway for gas transport. Gas diffusion in coal matrix is usually affected by both Knudsen diffusion and bulk diffusion. A theoretical pore-structure-based model was proposed to estimate the pressure-dependent diffusion coefficient for fractal porous coals. The proposed model dynamically integrates Knudsen and bulk diffusion influxes to define the overall gas transport process. Uniquely, the tortuosity factor derived from the fractal pore model allowed to quantitatively take the pore morphological complexity to define the diffusion for different coals. Both experimental and modeled results suggested that Knudsen diffusion dominated the gas influx at low pressure range ( 6 MPa). For intermediate pressure ranges (2.5–6 MPa), combined diffusion should be considered as a weighted sum of Knudsen and bulk diffusion, and the weighing factors directly depended on the Knudsen number. The proposed model was validated against experimental data, where the developed automated computer program based on the Unipore model can automatically and time-effectively estimate the diffusion coefficients with regressing to the pressure-time experimental data. The theoretical determined diffusion coefficients well predicted the pressure-dependent variations of the experimental measured diffusion coefficient for different coals. This theoretical model is the first-of-its-kind to link the realistic complex pore structure into diffusion coefficient based on the fractal theory. The experimental results and proposed model can be coupled into the commercially available simulator to predict the long-term CBM well production profiles.

The development of alternative to silicon carbide (SiC) holds great promise in energy and environmental related catalysis because the harsh preparation process and high cost limit its large-scale application. In this work, the core-shell structured ZnAl2O4@Al ceramic-metal composites (Zn-Al-T) are prepared from low cost metallic Al powder by a facile and environment-friendly approach to replace silicon carbide for Co-based Fischer-Tropsch synthesis (FTS, a typical strong exothermic heterogeneous catalytic reaction). The composition, thermal conductivity, surface chemical properties and pore configuration of the ZnAl2O4@Al composites can be easily modulated by controlling the calcination condition. Among Zn-Al-T composites, the Zn-Al-650 and Zn-Al-750 samples demonstrate optimum coupling of physicochemical properties, i.e., robust chemical stability, meso-macropore structure (wide mesopore and high macroporosity) and high thermal conductivity. Thus, the excellent FT performance (low CH4 selectivity and high selectivity to C5+) was obtained on the Co/Zn-Al-650 and Co/Zn-Al-750 catalysts. The heat transfer experiments were conducted on a special tubular fixed-bed reactor (I.D. = 22 mm) under near-industrial conditions. At similar reaction rates, the effective radial thermal conductivity coefficient (keaff) in the Co/Zn-Al-650 catalyst bed is 3–4 times and 1–2 times that in the Co/Al2O3 and Co/SiC catalyst beds respectively, resulting in a more uniform temperature distribution in Co/Zn-Al-650 catalyst bed. In addition, the ZnAl2O4@Al composite has wide application prospect in strong exothermic/endothermic catalytic system owing to its high thermal conductivity, adjustable physico-chemical properties, facile preparation method and low cost.

Investigations of mixing process, combustion and emission characteristics have been performed in a double-cone premixed burner under various mixing distances. The complex flow field and flame structure are accurately captured by the simulation model. The modified unmixedness coefficient, flame index, NO, CO emissions have been calculated and analyzed in detail. Numerical results show that the dimensionless mixing distance has a significant impact on the fuel mixing effect and then affects the high temperature zone position and emissions. With the increase of dimensionless mixing distance, the mixing process is mainly affected by the inner recirculation zone instead of the outer recirculation zone. The high temperature zone changes from the corner to the center. When the dimensionless mixing distance is 0.15, the peak concentration of CH2O and OH is below 1500 K, and the concentrations are relatively lower above 1500 K. The concentration scatter is relatively concentrated, which indicates that the mixing quality is the best and the reaction is the most uniform. The combustion mode is dominated by premixed combustion. When the dimensionless mixing distance is 0.1 and 0.2, regions with higher concentration of CH2O and OH still exist after 2000 K. The proportion of non-premixed combustion mode increases and the combustion temperature is high. NO and CO emissions first decrease and then increase with the increase of mixing distance from 0.1 to 0.2. According to the present analysis, the emission is the lowest when the dimensionless mixing distance is 0.15.

A high-sulfur (4.69 wt%) crude oil was discovered in the China Bohai Bay Basin which is known to contain low sulfur crude oil. The composition of this high sulfur crude oil and its geological origin are unknown. In this study, thiophenic and sulfidic sulfur compounds were isolated from the crude oil by methylation/demethylation and characterized using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and gas chromatography-mass spectrometry (GC–MS). Relatively high abundance of sulfur compounds with 30 carbon atoms and 5–7 double bond equivalence (DBE), which were assigned to sulfurated steranes with thiophene or tetrahydrothiophene moieties. Some of these compounds have not been reported in fossil fuels. In addition to commonly found sulfur compounds in petroleum feedstock, such as benzothiophenes and dibenzothiophenes, other structural sulfur compound types were detected: long-chain 2,5-di-n-alkylthiolanes, 2,5-di-n-alkylthianes, bicyclic terpenoid sulfides, isoprenoid thiophenes, and isoprenoid benzothiophenes. The presence of abundant biomarker sulfur compounds suggests that the sulfuration of the high sulfur crude oil was occurred in the early diagenesis stage instead of a thermochemical sulphate reduction (TSR) process.

This paper proposes a methodology to characterize the following petroleum properties: UOP characterization factor (K), nitrogen content, solubility parameter, sulfur content, maximum and minimum pour point, and kinematic viscosity (at 20 °C, 30 °C, 40 °C and 50 °C), in petroleum within a single 1H NMR (proton nuclear magnetic resonance) spectra. Multivariate calibration tools, such as partial least squares (PLS), orthogonal projections to latent structures (OPLS) (with variable selection), interval PLS (iPLS), synergy interval PLS (siPLS) and model population analysis (MPA), were applied to 138 samples. The models were evaluated by coefficient of determination (R2), root mean square error of prediction (RMSEP), and residuals. In general, model population analysis had better results in the determination of petroleum's physicochemical properties than PLS and OPS. Thus, MPA provided models with better accuracy in the determination of the following properties: UOP characterization factor (0.06), nitrogen content (0.048 wt%), kinematic viscosity at 40 °C (relative error of 21.9%) and pour point (14.58 °C and 19.2 °C, respectively). The sulfur content was estimated with a 0.09 wt% mean error of prediction, using the PLS model, and the solubility parameter with a 1.06 (MPa)1/2 mean error of prediction, using the OPLS model.

Mesoporous γ-Al2O3 materials with different channel properties were successfully synthesised by using cellulose nanofiber (CNF) as template. The corresponding NiMo catalysts were prepared and further evaluated in the hydrodesulfurization (HDS) of dibenzothiophene (DBT). The as-synthesised γ-Al2O3 supports and NiMo catalysts were characterized by XRD, nitrogen adsorption-desorption, H2-TPR, Raman, SEM, TEM, XPS and HRTEM techniques. The NiMo/MA-7 catalyst displayed the highest DBT conversion at all liquid hourly space velocities (LHSVs). At high LHSV of 150 h−1, DBT HDS efficiency over NiMo/MA-7 (∼30%) is about six times than that of the comparison catalyst NiMo/MA-0 (5%) without CNF addition. This outstanding performance attributed to synergistic effects of open mesoporous structure, appropriate dispersion and stacking morphology of active metals, and the suitable MSI (metal-support-interaction). In addition, the products distributions of all catalysts in the HDS of DBT were investigated, and it is found that HYD/DDS ratio was promoted after using CNF as template agent.

Particulate matter (PM) emissions have become an increasingly noticeable concern for gasoline vehicles, especially for gasoline direct injection (GDI) one. The PM index (PMI) model developed by Aikiwa et al. provides an effective model linking the fuel properties to the PM emissions from gasoline vehicles. In this study, a more practical reduced PM index (RPMI) was developed based on the detailed analysis of 22 fuels with various physical properties and chemical compositions. Two approaches of statistical mathematics of correlation analysis and multivariate linear regression (MLR) were adopted in the modeling process. The RPMI involving two global fuel properties of T90 (distillation temperature of 90% by volume) and T70 (distillation temperature of 70% by volume) was tested to be statistically valid. In addition, the model was verified through the engine bench tests and the vehicle emissions tests. The results reveal that the RPMI showed good correlations to the engine-out particle number (PN) emissions under all of the typical test conditions, including PFI (port fuel injection) mode, GDI (gasoline direct injection) mode and compound injection (PFI + GDI) mode. In addition, the RPMI demonstrated a significantly high correlation to vehicle-out PN emissions over the New European Driving Cycle (NEDC) with the determination coefficient R2 = 0.947. Moreover, a moderate correlation (R2 = 0.801) of the index to the filter PM mass emissions was observed. In the light of no additional components analysis is needed except for the legitimate tests of fuels, the RPMI has the potential to be a useful tool for original equipment manufacturers (OEMs) and environmental certification departments to expediently evaluate the fuel effect on PM emissions.

Non-isothermal kinetics involved during the slow pyrolysis of waste biomass (sawdust) was investigated. The slow pyrolysis profile of sawdust was distinguished into three reactions corresponding to each pseudo component (hemicellulose, cellulose & lignin) through the deconvolution process. Kinetic triplets (activation energy, reaction mechanism & pre-exponential factor) were estimated for each pseudo component. The Straink (SR) and Friedman (FR) iso-conversional kinetic models were used to calculate the activation energy of pseudo-cellulose (SR = 162.90 kJ/mol, FR = 165.67 kJ/mol), pseudo-hemicellulose (SR = 156.25 kJ/mol, FR = 158.47 kJ/mol) and pseudo-lignin (SR = 301.62 kJ/mol, FR = 316.72 kJ/mol). The reaction mechanism involved during the slow pyrolysis of waste sawdust was identified through integral master plot method. The results revealed that the two-dimensional contract area (R2) and second order reaction (F2) reaction mechanism dominates slow pyrolysis of pseudo-cellulose and pseudo-hemicellulose, respectively. However, no exact reaction mechanism was observed for pseudo-lignin. The pre-exponential factor was determined with the help of the activation energy and reaction mechanism. Thermodynamic parameters i.e. change in enthalpy ( Δ H ), entropy ( Δ S ) and Gibb’s free energy ( Δ G ) were also determined for pseudo-cellulose ( Δ H = 157.54 k J / m o l , Δ S = - 17.615 J/mol and Δ G = 168.64 kJ/mol) and pseudo-hemicellulose ( Δ H = 151.28 k J / m o l , Δ S = 6.61 J/mol and Δ G = 147.12 kJ/mol).

In-depth knowledge on pyrolysis behavior of lignocellulosic biomass is pivotal for efficient design, optimization, and control of thermochemical biofuel production processes. Experimental thermogravimetric analysis (TGA) is usually employed to peruse the pyrolysis kinetics of biomass samples. In addition to that, the main constituents of biomass (i.e., cellulose, hemicellulose, lignin) as well as the process heating rate can excellently reflect its pyrolysis characteristics through modeling techniques. However, the application of statistical and phenomenological models for extremely complex and highly nonlinear phenomena like lignocellulose pyrolysis is challenging. To address this challenge, adaptive network-based fuzzy inference system (ANFIS) was consolidated with particle swarm optimization (PSO) algorithm to prognosticate the kinetic constants of lignocellulose pyrolysis. More specifically, the PSO algorithm was applied to tune membership function parameters of the ANFIS model. Three ANFIS−PSO topologies were designed and trained to estimate the kinetic constants of lignocellulose pyrolysis, i.e., energy of activation, pre-exponential coefficient, and order of reaction. The input variables of the developed models were biomass main constituents and the process heating rate. The developed models could predict the kinetic constants of lignocellulosic biomass pyrolysis with an R2 > 0.970, an MAPE 0.91 using the developed models, further confirming their fidelity. Overall, the lignocellulose pyrolysis behavior could be reliably and accurately estimated using the trained ANFIS–PSO approaches as an alternative to the TGA measurements. In order to make practical use of the trained models, a handy freely-accessible software platform was designed using the selected ANFIS−PSO models for approximating biomass pyrolysis kinetics.

In order to study the influence of surfactant on pore fractal characteristics of composite acidized coal. In this paper, the coal samples were acidified by solution constituted with the Sodium Dodecyl Sulfate (SDS), hydrochloric acid (HCL) and hydrofluoric acid (HF). And the proximate and ultimate analysis, X-ray diffraction (XRD) testing, scanning electron microscopy/energy dispersive spectroscopy (SEM-EDS) and nuclear magnetic resonance (NMR) testing were carried out. The fractal dimension of pore in coal was evaluated by fractal theory, and the evolution relationship between coal quality, NMR fractal features and coal pore structure parameters were characterized. The results show that the addition of surfactant has a great influence on the coal characters. The mineral content in coal is exponential positively correlated with the fractal dimension (Ds) of seepage pores. The relative content of ash is linear positively correlated with the fractal dimension. Conversely, the volatiles is linear negatively correlated with the fractal dimension. SDS synergistic acidification compared to without SDS, the fractal dimension (Dw) of the total pore distribution and the fractal dimension (Ds) of the seepage pores are both reduced, indicated that the addition of SDS promotes the improvement of coal pore connectivity by acidification treatment. The results showed that after SDS synergistic acidification, the proportion of seepage pore volume was increased by 5.99%, and the fractal dimension is linear negatively correlated with the porosity. The changes of these parameters are beneficial to the seepage, migration and extraction of coalbed methane. Therefore, SDS synergistic composite acid fracturing technology has practical guiding significance for improving acid fracturing effect and increasing coal seam permeability. The research results are of great significance for improving the efficiency of coalbed methane mining and reducing coalbed methane pollution.

Injection of gas mixtures (CO2, N2) into coal seams is an efficient method to both reduce CO2 emissions and increase the recovery of coalbed methane. This process involves a series of complex interactions between ternary gases (CH4, CO2, and N2) co-adsorption on coals, mass transport of two-phase flow, together with heat transfer and coal deformation. We develop an improved thermo-hydro-mechanical (THM) model coupling these responses for gas mixture enhanced CBM recovery (GM-ECBM). The model is first validated, and then applied to simulate and explore the evolution of key parameters during GM-ECBM recovery. Schedules of constant- and variable-composition injection are optimized to maximize CH4 recovery and CO2 sequestration. Result shows that the injected gas mixture displaces CH4 through competitive sorption and accelerates the transport of CH4 within the coal seam. The consistency between the modelling and field results verifies the feasibility and fidelity of the THM model for effective simulation key processes in GM-ECBM. Permeability evolution is strongly influenced by the combined effects of CH4 desorption induced matrix shrinkage, CO2/N2 adsorption induced matrix swelling, thermal strains, and compaction induced by changes in effective stress. During ECBM, reservoir permeability first increases due to pressure depletion and CH4 desorption, then dramatically decreases due to matrix swelling activated by the arrival of the CO2/N2 mixture. CH4 pressure decreases rapidly at early time due to displacement by the injected gas mixture, and then deceases slowly in the later stage. The sweep of N2 accelerates CH4 desorption and subsequent transport, and hence promotes a decrease in reservoir temperatures distant from the injection well even prior to the arrival of CO2. CH4 production rate during GM-ECBM exhibits a decline-increase-decline trend and usually has an elevated but delayed CH4 production peak compared to primary recovery. A higher CO2 Langmuir strain constant reduces the critical CO2 composition in the injected mixture when reaching the threshold of well shut down. An improved balance between early threshold (N2) and large matrix swelling (CO2) can be achieved by injection beginning with low CO2 composition and following with a sequential increase of CO2 composition. In studied cases, the gas recovery ratio of the optimal variable-composition case reaches 68.4% compared to of 59.4% pure CO2 and 64.2% of optimal constant-composition cases, indicating a higher efficiency of variable-composition injection.

The issue of utilizing multi-fuels for enhancing the burning process in the “Homogeneous charge compression ignition” HCCI engine cylinder has been developing significantly during the last decades. This technique has established to overcome the difficulties of the engine ignition and knock-like combustion control when distinguished with utilizing a single fuel during the engine management system. Furthermore, the developing concern towards the cleaner environment and the battle against wonderful weather by using the renewable fuel types are urgently required. In this research, the theoretical and experimental study will achieve the possibility of preparing a charged mixture, which consists of the air and three different kinds of alternative fuels. The prepared mixture was introducing into a mixing chamber near the intake manifold of the HCCI engine working at varying load conditions. Those fuels were the natural gas, hydrogen, and “Dimethyl ether” as a biodiesel fuel. The mixture has been utilizing to enhance the HCCI engine performance. However, the non-petroleum based alternative fuel such as “Dimethyl ether” DME has been used as an additive to the mixes of the natural gas or natural gas/hydrogen blends. Current methodology has been acquainting to make the chance of the engine ignition control is accessible, alongside its advantages to keeping away from the engine knocking or misfire operation. The ideal dose of each type of the tri-fuels composition with different percentages of each fuel used has been optimizing. Natural gas fuel is the primary fuel of the engine, and the other two types of fuel have used as additives for renewable fuels. The obtained results showed that there are certain proportions for each kind of the employed fuel in which the possibility of the engine operation without the occurrence of the knock-like combustion or the apparent of misfire operation have been achieving.

The fused aromatic rings (FARs) of coal are considered to be relatively stable during coalification. However, it is speculated that defects may form in FARs during the deformation of coals under tectonic stress. In order to investigate the possibly existed mechanolysis reactions of FARs, we performed molecular dynamics simulations with the reactive force field to study an anthracite coal model under shear stress. The results show that the FAR rupture reactions occur much more efficiently than expected. There are two important ways to initiate FAR rupture: attacked rupture and direct rupture. Among the mechanisms, two types of rearrangement reactions play crucial roles. The first type is intra-ring rearrangement where the FAR forms a three-membered ring and a five-membered ring before rupture. The second type is extra-ring rearrangement where the location of substituent group changes. Both rearrangement reactions determine which bond in the FAR preferentially breaks but in different manners, and then promote the subsequent reactions. Comparing to pyrolysis mechanism, mechanolysis mechanism follows completely different reaction pathways and result in different products. This research will aid in understanding the reaction mechanisms of coal mechanochemistry, and it opposes the traditional standpoint that the FARs of coal are relatively stable and very hard to be destroyed during coalification.

High-iron coal is widely distributed throughout China and could be used as the feedstock for slagging gasifiers. To enable cleaner, efficient, large-scale use of high-iron coal by the slagging gasifier, a solid understanding of coal ash fusion behaviour is required. In this study, we investigated the fusion behaviour of synthetic high-iron coal ash (SiO2-Al2O3-Fe2O3-CaO) using an ash fusion temperature (AFT) analyser, X-ray diffractometer (XRD), differential scanning calorimeter (DSC) and thermodynamic modelling. We found that AFTs decreased with increasing α values (CaO/(SiO2 + Al2O3), mass ratio) due to the formation of low-melting-point minerals. AFTs also decreased with increasing S/A (SiO2/Al2O3, mass ratio), attributed to massive generation of the amorphous phase. The ash fusion process is described with three stages, namely, the mineral transformation, formation of the initial liquid phase, and melting of the residual solid phase. In the first stage, the mineral species was considered as the key parameter, and the increase in α and S/A favoured the formation of mineral with a low melting point. S/A also significantly influenced the second stage, with greater S/A ratios correlating with lower temperature and higher content of the initial liquid phase. In contrast, the third stage was accelerated by intense mass transfer, as the viscosity of the liquid phase dropped dramatically with increasing α value. The fusion heat corresponding to the melting of minerals at high temperature showed a negatively linear correlation with the flow temperature of synthetic coal ash, which may provide an alternative method of predicting the flow temperature of real coal ash.

Continuously growing world’s energy demand and global climate change due to green house gas emissions have created need to find out renewable and sustainable energy solution. Biodiesel is one of the most promising substitute of diesel fuel that can be produced from vegetable oils, animal fats, waste oils etc. It is broadly classified in four generations i.e. edible oils (first generation), non-edible oils (second generation), waste oils (third generation) and advance solar biodiesel (fourth generation). There are some limitations associated with biodiesel as a fuel in diesel engines like cold flow, oxidation stability etc. Selection of biodiesel due to the above reasons is region specific and depends on the specific properties which are mainly governed by fatty acid composition of that oil. This review discusses the physicochemical properties of different generation biodiesel using 52 types of feedstocks. The chemical composition and physicochemical properties of 31 raw oils have also been discussed. As different fatty acid methyl esters (FAME) structures behave differently, it is not possible to develop a unique approach for obtaining optimum composition of FAME. The low concentration of polyunsaturated FAME and long-chain saturated FAME is more favorable for oxidation stability, low-temperature operability, and satisfactory performance. American Society for Testing and Materials (ASTM), European committee for standardization (CEN), Bureau of Indian Standards (BIS), etc. provided the specifications for the biodiesel and their blends.

The performances of the primary catalysts olivine, dolomite, γ-alumina and FCC spent catalyst were evaluated in the continuous steam gasification of sawdust in a bench-scale plant equipped with a fountain confined conical spouted bed reactor. The experiments were carried out at 850 °C, and the efficiency of the gasification process was defined by gas yield, H2 production, tar concentration and composition, and carbon conversion efficiency. The benefits of the fountain confiner not only helped to improve the gas-solid contact, and therefore favoured the primary catalysts’ reforming and cracking activity, but also enhanced H2 production and reduce tar formation. Thus, dolomite and γ-alumina recorded the lowest values of tar, 5.0 and 6.7 g Nm−3, respectively, which corresponded to 79% and 72% tar reduction compared to the inert sand, whereas olivine and the FCC spent catalyst recorded higher tar contents, 20.6 and 16.2 g Nm−3, respectively. It is noteworthy that light PAHs were the most abundant species in the tar (60 wt% of the whole tar content).