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Hydrochar was produced from sewage sludge via the hydrothermal carbonization (HTC) process. The effects of carbonization temperature (150–300 °C), solid load (10–30%), and reaction time (30–120 min) were investigated using response surface methodology (RSM) based on the Box-Behnken factorial design. The optimum operating conditions for hydrochar production were determined by maximizing three key responses: solid yield, higher heating value (HHV), and energy yield. The results showed that the HTC process increased the carbon content from 30.02 wt.% to 37.53 wt.% while decreasing the hydrogen content from 5.26 wt.% to 3.18 wt.% and oxygen content from 25.55 wt.% to 9.48 wt.%, affecting the HHV and energy yield of the hydrochar. As for the optimization, the findings indicate the suitability of a quadratic model, revealing the most favorable conditions to be the temperature of 150 °C, the solid load of 30%, and the reaction time of 30 min, resulting in hydrochar with a solid yield of 71.24%, an HHV of 17.90 MJ/kg, and an energy yield of 94.81%. Of all the process parameters, temperature had the most significant influence on all responses. Further characterization using Fourier transform infrared spectroscopy (FTIR) demonstrated enhanced conversion of sewage sludge to hydrochar, evidenced by a notable reduction in peak intensities of solid product compared to the parent material. Scanning electron microscopy (SEM) analysis confirmed structural and porosity changes in sewage sludge post-HTC treatment. Thermogravimetric analysis (TGA) indicated remarkable improvements in the combustion performance of hydrochar, including increased ignition temperature (241.91 °C) and burnout temperature (688 °C). The results of this optimization study offer valuable insights for the scalable implementation of the HTC process in efficiently producing solid fuel from sewage sludge.

This study used response surface methodology (RSM) and artificial neural network (ANN) to predict and optimize lithium polysulfide (LiP) adsorption on nitrogen-doped activated carbon (NDAC). Firstly, the NDAC production from palm kernel shell was optimized using RSM, where statistical analysis indicated the best conditions to be an impregnation ratio (IR) of 2.0, an activation temperature of 880 °C, and an activation time of 80 min—with IR having the most significant impact on LiP adsorption. Experimental results from the RSM were then used to train the predictive capabilities of the ANN for LiP adsorption. Although both approaches effectively predicted the adsorption process, ANN exhibited a superior prediction accuracy, characterized by a higher coefficient of determination (R2) and a lower mean square error (MSE). The NDAC synthesized under optimized conditions was subsequently made into a cathode composite with sulfur (NDAC/S) and evaluated for its performance in a lithium‑sulfur (Li-S) battery. Experimental data indicated that the Li-S coin cell battery consisting of NDAC/S had a remarkable initial specific capacity of 1054.96 mAh/g and maintained a favorable capacity retention of 66 % after 100 cycles at 0.1C. This outstanding electrochemical performance is attributed to the synergistic effect of a hierarchical pore structure, large surface area, substantial pore volume, and the presence of doped nitrogen that provides strong chemical bonding with LiP.

Thermal–chemical conversion is needed to improve the quality of bio-oil. When bio-oil is heated, it polymerizes to form coke, causing severe problems to its upgrading processes and thus hindering its further utilization. As stable free radicals are generated and attached to coke during the active radical polymerization of bio-oil, figuring out the evolution of stable free radicals is a key to revealing the coke formation mechanisms. In this study, bio-oil pyrolysis was conducted between 300 and 600 °C, coupled with in situ electron paramagnetic resonance (EPR) detection. The results indicate that the stable free radicals generated during pyrolysis are related to bio-oil polymerization and coke structure change. In the heating stage, the stable free radicals are generated from the polymerization of bio-oil and the condensation of coke, and the process can be expressed by two first-order kinetics with activation energies of 14.57 and 10.51 kJ/mol, respectively. The aromatic structure stable radicals are generated mainly by the polymerization of bio-oil with an activation energy of 12.66 kJ/mol. In the cooling stage, the free radical reaction would be caused by coke shrinkage, leading to further changes in coke structure.

This study aims to convert oily sludge (OS) into oily sludge char (OSC) by pyrolysis and microwave-induced pyrolysis. The operating parameters affecting the production of chars from OS by pyrolysis (temperature (200–800 °C) and residence time (30–150 min)) and microwave-induced pyrolysis (microwave power (200–800 W) and irradiation time (5–25 min)) were investigated. The tools used to identify the physiochemical properties of the best products were Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscope (SEM), and thermogravimetric and derivative thermogravimetric analysis (TGA-DTG). Energy characteristics including higher heating values (HHV), proximate analysis, element composition, and H/C and O/C atomic ratios were explored. The OSC produced by pyrolysis at a temperature of 600 °C and residence time of 90 min (labeled as OSC-Py@600–90) achieved the highest HHV (22.95 MJ/kg), while the OSC produced by microwave at a microwave power of 800 W and irradiation time of 10 min (labeled as OSC-MW@800–10) achieved the highest HHV (28.33 MJ/kg). The BET surface area of OS, OSC-Py@600–90, and OSC-MW@800–10 are OS 29.56 m2/g, 81.33 m2/g, and 238.52 m2/g, respectively. The data of the current study clarified that the OSCs produced from OS by pyrolysis and microwave processes could be used for energy generation.

With the depletion of fossil fuel reserves and the increasing concern about greenhouse gas emission, the need to develop technologies for using renewable and sustainable energy resources is becoming urgent. Solar, winds, geothermal, and hydro as well as nuclear energy are all considered as clean energy sources to (partially) substitute fossil fuels in energy generation. Biomass, however, remains the only renewable energy source consisting of hydrocarbon compounds, which is a necessity for making basic building blocks for chemical industries. The development of feasible gasification technologies to produce syngas (primarily H2and CO) is considerably inhibited by the “tar issues”. The tar content in the product gas has to be extremely low in order to effectively use the gas downstream, such as for synthesizing liquid fuels and generating electricity. Although there are a wide range of options for removing, cracking, and catalyzing the tar, this review mainly discusses the catalytic reforming approach using char as catalysts, of which the importance of the carbon structure of chars will be underpinned because the char structure including matrix carbon structure and functional groups on the char surface not only affects the reactivity of nonmetal active sites but also largely dominates the role/fate of internally existing and externally added metal species.

This study investigated the characteristics of NO emissions during oxy-coal combustion with wet-recycle, especially in the presence of high H2O concentrations. The oxy-combustion was carried out using two types of coal, namely Leiyang (LY) anthracite and Zhundong (ZD) bituminous coals, inside a 24 kW drop tube furnace under different O2/CO2/H2O atmospheres. The results showed that the NO conversion increased with decreasing CO2concentration from 70% to 30% and decreased with increasing H2O concentration from 10% to 40%. Under the experimental conditions employed in this study, the fuel-N conversion for both LY and ZD coals under the oxy-coal wet recycled combustion was lower than that under the oxy-coal dry recycled combustion. The results indicated that H2O and CO2showed a competitive effect on NO emissions, though both of them have positive effect on NO reduction. In order to investigate the effects of H2O/CO2on recycled NO, oxy-coal combustion experiments were also performed with the initial addition of NO concentrations of 900 ppmv. The results showed that NO reduction ratio in O2/CO2was lower than that in O2/CO2/H2O for both coals under our experimental conditions. It is believed that the results of this study can provide some fundamental information on the effect of H2O/CO2on the characteristics of NO emissions during oxy-coal combustion with wet-recycle.

As an eco-friendly, cheap and readily available material, calcium-based oxides could play the dual roles of both tar reforming catalyst and CO2sorbent, thereby producing hydrogen-rich gas with low tar concentration and low carbon emission during steam gasification of coal/biomass. This study aimed to experimentally investigate effects of different parameters on hydrogen-rich gas production during steam gasification of lignite using dual calcium-based catalysts. Furthermore, in view of the importance of the water–gas shift reaction to hydrogen-rich gas production, its catalytic kinetics with the homemade calcium sorbent was also studied. The results show that the addition of active calcium oxide remarkably decreased tar yield, leading to a significant increase of noncondensable gas yield. Increase of loading amount of homemade sorbent enhanced CO2absorption, thereby breaking the water–gas shift reaction equilibrium and shifting it, resulting in a distinct increase of H2yield and a decrease of CO yield. The highest H2yield of 1.24 N m3/kg-coal was obtained in current study. Finally, the catalytic kinetics of the water–gas shift reaction with homemade sorbent were obtained using a newly developed and more precise kinetic model, and from there the conversion of the WGS reaction was well predicted by the new kinetic model.

To understand the mercury speciation and mass flow in a full-scale bituminous coal-fired power plant equipped with a selective catalytic reduction (SCR) unit, an electrostatic precipitator (ESP), and a seawater flue gas desulfurization (SWFGD) scrubber, the evolution and emission of mercury was systematically measured and analyzed. The results showed that the elemental mercury (Hg0) was oxidized mainly through heterogeneous oxidation, especially in SCR, which transformed 57–64% of elemental mercury (Hg0) to oxidized mercury (Hg2+). It changed the concentrations of different mercury species and then increased the Hg2+removal efficiencies of SWFGD, which ranged from 67 to 82%. A total of 8.24–11.54% of mercury was adsorbed by fly ash to form particulate-bound mercury (HgP) and subsequently removed by the ESP. Mass flow and mass distribution of mercury indicated that most mercury was removed and retained in the SWFGD. The heterogeneous oxidation of Hg0in SCR and then absorption of Hg2+by SWFGD significantly enhanced the mercury removal in the studied coal-fired power plant, although a part of Hg2+absorbed in SWFGD was reduced and released back to the flue gas. Hg2+was a little more than Hg0in the flue gas emitted to the atmosphere. In addition, the SWFGD system without limestone addition may be beneficial for decreasing the re-emission of Hg0. The mercury emission factor at the power plant is 4.098 g/TJ, which is lower than that at other power plants without SCR. The configuration of SCR + ESP + SWFGD enhances the co-benefit mercury control.

Single and mixed coconut shell (CS) and palm kernel shell (PKS) were successfully converted to activated carbon by using potassium hydroxide (KOH) as activating agent. Mixed activated carbon was produced from coconut shell: palm kernel shell at different KOH concentrations of 30%, 40% and 50%. Activation process was performed in a conventional microwave oven at fixed power and time of 600W and 20 minutes respectively. The results showed that activated carbon produced from single and mixed biomass at 40% concentration of KOH exhibited higher adsorption capacity for iodine number and percentage removal of MB with comparison to 30% and 50% of KOH concentrations. The highest BET surface area of 441.19 m2/g was obtained by CSAc-40. Further both CSAc-40 and PKSAc-40 produced an average pore size diameter of less than 2.0 nm which is in the range of micropore region. On contrary, the mixed CSPKSAc-40 produced an average pore size diameter of 6.0 nm which is in the region of mesopore. All the CSAc-40, PKSAc-40 and mixed CSPKSAc-40 showed similar adsorption trend for iodine number and percentage removal of MB. Interestingly, this finding showed that in the mixed activated carbon some chemical reactions might have occurred during the activation process producing mesoporous instead of microporous as obtained by the single biomass activated carbon.

Calcium-based sorbent is a suitable sorbent for the solid looping CO2capture. The loss-in-capacity due to sintering, however, poses a big problem to the direct utilization of natural/pure CaO in the looping process. The issue of attrition, meanwhile, adds a further obstacle to the long-term cyclic utilization of the sorbent. Additionally, the performance of CaO-based sorbent in the long term solid looping CO2capture depends to a great degree on the type of precursor used to derive the sorbent. This study aims to systematically study the influence of the various calcium precursors on the sorbent performance in the long term carbonation-calcination cycles. Results of this study indicate that the absorption capacity of CaO sorbents was influenced significantly by the type of CaO precursor. It was found that CaO sorbent derived from calcium acetate gave the best absorption capacity of 0.61 mol-CO2/mol-sorbent after 48 carbonation/calcination cycles. The addition of inert supporting matrix of Al2O3has enhanced sintering resistance of the sorbents. The X-ray diffraction (XRD) results, supported with scanning electron microscopy (SEM) observations and N2adsorption/desorption analysis, suggest that the formation of mayenite (Ca12Al14O33) helped to strengthen the framework of the sorbents, consequently improved sintering resistance and long-term cyclic stability of the modified sorbents. The incorporation of calcium aluminate cement decreased the attrition of sorbents, over the 48 cycles of carbonation and calcination, from 24.6% to 7.4%. Finally, in this study, carbonation kinetics of the sorbent was studied using a new, more precise three-stage carbonation kinetic model. The calculated results fitted to the experimental results very well.

The combustion of bituminous coal, bio-oil, and their slurry mixtures were performed under air atmosphere using Thermogravimetric Analyzer (TGA). All samples were run from room temperature to 110°C and held for 10 minutes before the temperature was ramped to 1100°C and held again for 10 minutes at 1100°C at the heating rate of 10°C/min and gas flow rate of 50mL/min. Kinetic evaluation was conducted using a simple Arrhenius-type kinetic model with first-order decomposition reaction. Apparent activation energy, Ea, and pre-exponential factor, A, were calculated from the modelling equation. Results reveal that the reactivity of CBS fuel is higher than a single coal fuel to which the addition of bio-oil helps to increase the combustion performance of the blends. The optimum fuel ratio appears at 50:50 ratio with equal contribution of coal and bio-oil properties that contribute to the increase in volatile matter causing maximum combustion rate achievable at much lower temperature compared to single coal fuel.

In this paper, the formation, characterizaton, properties and applications of nanoemulsions are reviewed and summarized. Nanoemulsions are under extensive investigation as it can aid to recover the residual oil from reservoir rock in Oil Recovery application because of the submicron sized emulsion. Nanoemulsion is thermodynamically or kinetically stable system in which two or more immiscible phases that is made up at least one phase dispersed in others by mechanical shearing with appropriate surfactants. Nanoemulsions possess stability against creaming or sedimentation due to their small particle size while Ostwald ripening forming the main mechanism of nanoemulsion breakdown. Nanoemulsion has droplet sizes of the internal phase less than 500nm. Particle size and surface properties of droplets of nanoemulsion plays an important factor in the biological behavior of the formulation. Nanoemulsion shows great promise for the future of oil industries and biotechnologies, cosmetics and drug therapies.

Combustion behaviour study of coal-biooil slurry (CBS) fuel prepared at different ratios was conducted using Thermogravimetric Analyzer (TGA). The materials comprised of Clermont bituminous coal (Australia) and bio-oil, derived from Empty Fruit Bunch (EFB) by means of fast pyrolysis. The samples were heated from room temperature to 110°C and held for 10 minutes before the temperature was ramped to 1100°C and held for another 10 minutes at constant heating rate of 10°C/min under air atmosphere at constant flow rate of 50 mL/min. The proportions of CBS fuel at 50:50 blends were observed to have significant influence on the combustibility of the slurry blends. The addition of bio-oil will shifted the ignition temperature towards early devolatilization. Meanwhile, the DTG profiles of the blends, showed decomposition of VM and char indicating bio-oil to be more reactive than coal with highest degradation rate appears at the blend ratio of 50:50 biooil/coal. These findings could be useful to introduce a new application of bio-oil in energy mix generation into coal mixture to cater for coal consumption reduction strategy for future application in vast existing conventional power plants.

The objective of this study is to investigate the ability of Elaeis guineensis fruit fiber or known as oil palm mesocarp fiber (OPMF) to adsorb nickel from aqueous solution. As one of the major oil palm producer, Malaysia has abundantly oil palm waste that potentially be used as biosorbent. Limited studies used OPMF as biosorbent to remove nickel, thus it was used in this study. The effects of pH, initial metal concentration and contact time on nickel uptake were studied. The OPMF was soaked in nickel nitrate aqueous solution and the Ni-loaded OPMF being digested to analyse the nickel concentration by using ICP-OES. The adsorption was investigated in the pH range of 2.0-8.0 and the optimum pH for nickel removal was found to be 7.0. The contact time was varied between 5 to 120 mins and the nickel adsorption was found to achieve equilibrium in a very short time (i.e.<5 mins). The percentage of nickel removal decreased from 3.3 to 1.7 % with increasing nickel concentration from 505 to 1683 mg/L. The adsorption isotherm was fitted well using Langmuir model with correlation coefficient, R2 of 0.98. The kinetic studies showed that the pseudo-second order model is the best model with the correlation coefficients of > 0.99 for all concentrations. Overall, the adsorption of nickel by OPMF gave positive results and the used of OPMF as biosorbent has great potential to be applied in the future.

Four types of biomass were characterized to investigate its metal adsorption capacity. The biomass were soaked in with nickel and cobalt solutions to examine the effect of biomass to amount of metal adsorbed. Oil palm mesocarp fibre (OPMF), empty fruit bunch (EFB), palm kernel shell (PKS) and sawdust were used in this study. Among all the biomass studied, oil palm mesocarp fibre shows the highest adsorption capacity with 1.8 mg/g and 1.6 mg/g of nickel and cobalt uptake, respectively. The metals adsorbed on the biomass were found to disperse into nanosize range.

•Radical reactions dominate the coke formation during the pyrolysis of bio-oil.•Radicals generated from bio-oil pyrolysis was proportional to temperature.•The coke formation was strongly inhibited when stopped the radical recombination.

Dry reforming of methane (DRM) promises to reduce greenhouse gas emission by converting CO2and CH4(produced e.g. in anaerobic digestion processes) into syngas with an almost equimolar H2/CO ratio suitable for use in Fischer–Tropsch (FT) synthesis for the production of varieties of high value chemicals and liquid fuels. Ni-based catalyst is the most viable catalyst to catalyse the reaction, but its use faces a great challenge due to its propensity to form and accumulate carbonaceous materials on its active surface. In this article, the mechanisms involved in the deactivation of Ni-based catalyst in DRM reaction by carbon deposition and other carbon-induced deactivation mechanisms, which understanding is vital for the improvement of the process, are reviewed. Based on a thorough assessment of literature, perspectives are given on ways to control and mitigate carbon deposition problems related to the use of Ni-based catalysts in DRM by means of manipulating reaction conditions and process parameters as well as through designing and developing the highly active coke-resistant Ni-based catalysts.