Fuel Processing Technology (v.137, #C)

Using sewage sludge as a denitration agent and secondary fuel in a cement plant: A case study by Ping Fang; Zi-Jun Tang; Jian-Hang Huang; Chao-Ping Cen; Zhi-Xiong Tang; Xiong-Bo Chen (1-7).
The influences of sludge feed rate, feed point, feed method, and air-staged combustion were systematically investigated in a Chinese cement plant with emphasis on NOX removal. Results indicate that the use of sludge as a secondary fuel is conducive to NOX reduction, which depends primarily on the feed rate and feed point. Moreover, both feed method and air-staged combustion influence NOX removal to some extent. Nonetheless, these factors have little effects on CO removal. When the sludge feed rate is 9 t·h− 1 in a precalciner reburning zone in the combustion temperature range from 850 to 1000 °C, NOX removal reached 75.82% in the air-staged combustion condition. The NOX concentration easily met the national emission standards. Finally, the use of sludge as alternative fuel does not affect clinker quality negatively. This method utilizes sludge effectively and reduces NOX emissions; hence, the application of sewage sludge as a denitration agent and secondary fuel in cement production is a worthy option.
Keywords: Sewage sludge; Denitration agent; Secondary fuel; Cement production;

Simultaneous removal of SO2 and NO by a vaporized enhanced-Fenton reagent by Yi Zhao; Run-Long Hao; Qing Guo; Ya-Nan Feng (8-15).
A novel integrative process for simultaneously removing SO2 and NO from coal-fired flue gas was designed, in which, SO2 and NO, especially NO, were initially oxidized by a vaporized enhanced-Fenton reagent (EF) made up of hydrogen peroxide, peroxyacetic acid, and ferrous sulfate, and then absorbed by Ca(OH)2 that followed. The experimental results indicated that the removal of NO was significantly affected by the adding rate of EF solution, the flue gas residence time, and the pH of EF solution, and slightly affected by the reaction temperature and the concentration of SO2. Under the optimal reaction conditions, the simultaneous removal efficiencies of 100% for SO2 and 89.2% for NO were obtained. Meanwhile, the reaction mechanism of simultaneous removal of SO2 and NO was speculated based on the related literature references and the characterizations of removal product by scanning electron microscope, energy dispersive X-ray spectrometer, and X-ray diffraction.
Keywords: Enhanced-Fenton reagent; Peroxyacetic acid; Simultaneous removal of SO2 and NO; Reaction mechanism;

Large scale biomass utilisation in energy-related applications is of paramount importance to reduce the fossil CO2 emissions. At European level, about a third of energy consumption is expected to be covered by renewables in the next 15 years. In addition, the CO2 emissions need to be reduced by 40% compared to the 1990 level. Within this context, innovative energy-efficient low carbon technologies have to be developed. Chemical looping is a promising conversion option to deliver reduced energy and cost penalties for CO2 capture.This paper assesses biomass direct chemical looping (BDCL) concept for hydrogen and power co-production. The concept is illustrated using an ilmenite-based system to produce 400–500 MW net power with flexible hydrogen output (up to 200 MWth). The performances are assessed through computational methods, with the mass and energy balances being used for in-depth techno-economic analysis. The biomass direct chemical looping delivers both high energy efficiencies (~ 42% net efficiency) with almost total carbon capture rate (> 99%) compared to other CO2 capture options (e.g. gas–liquid absorption). The economic parameters show also a reduced CO2 capture cost penalty for biomass direct chemical looping technology compared to gas–liquid absorption (e.g. 7% reduction of specific capital investment).
Keywords: Carbon capture utilisation and storage (CCUS); Biomass direct chemical looping (BDCL); Techno-economic and environmental assessments;

Syngas/H2 production from bioethanol in a continuous chemical-looping reforming prototype by F. García-Labiano; E. García-Díez; L.F. de Diego; A. Serrano; A. Abad; P. Gayán; J. Adánez; J.A.C. Ruíz (24-30).
Chemical-looping reforming (CLR) allows H2 production without CO2 emissions into the atmosphere. The use of a renewable fuel, bioethanol, in an auto-thermal CLR process has the advantage to produce H2 with negative CO2 emissions. This work presents the experimental results obtained in a continuously operating CLR unit (1 kWth) using ethanol as fuel. Two NiO-based oxygen carriers were used during more than 50 h of operation. The influence of variables such as temperature, water-to-fuel and oxygen-to-fuel molar ratios was analysed. Full conversion of ethanol was accomplished and carbon formation was easily avoided. A syngas composed of ≈ 61 vol.% H2, ≈ 32 vol.% CO, ≈ 5 vol.% CO2 and ≈ 2 vol.% CH4 was reached at auto-thermal conditions for both materials. Gas composition was closed to the given by the thermodynamic equilibrium. These results demonstrate the technical viability of H2/syngas production by using bioethanol in an auto-thermal CLR process.Display Omitted
Keywords: Hydrogen; Chemical-looping reforming; Bioethanol; CO2 emissions;

Preliminary experimental study on biofuel production by deoxygenation of Jatropha oil by Max Romero; Andrea Pizzi; Giuseppe Toscano; Alessandro A. Casazza; Guido Busca; Barbara Bosio; Elisabetta Arato (31-37).
Deoxygenation through decarboxylation of Jatropha curcas (non-edible) oil under a nitrogen atmosphere was performed using alumina (Puralox SBa200) and hydrotalcite (Pural MG70) as catalysts at 350 and 400 °C. In general, liquid product yields obtained exceeded 80%. FTIR spectroscopy showed that the oxygen contained in the liquid product decreases significantly when hydrotalcite is used as the catalyst with a reaction time of 6 h. At the end of the tests, a liquid biofuel was produced with a high proportion of hydrocarbons – around 83% – of mainly C8–C18. The product also showed good properties as a heating value of around 44 MJ/kg, higher than biodiesel (40 MJ/kg) and near to diesel (46 MJ/kg), and a lower viscosity (4 cSt) than biodiesel (4.5 cSt). Using GC analysis it was possible to identify the CO2 and CO as the principal compounds present in the reaction gas, confirming that oxygen is removed mainly through decarboxylation and decarbonylation reactions.
Keywords: Jatropha oil; Decarboxylation; Hydrotalcite; Hydrocarbon biofuel;

Activity and thermal stability of Pt/Ce0.64Mn0.16R0.2O x (R = Al, Zr, La, or Y) for soot and NO oxidation by Hai-Long Zhang; Yi Zhu; Shi-Dan Wang; Ming Zhao; Mao-Chu Gong; Yao-Qiang Chen (38-47).
In this study, Al2O3, ZrO2, La2O3, and Y2O3 were separately introduced into Pt/CeO2-MnO x catalyst to improve the thermal stability of catalysts and obtain a better soot and NO oxidation activity after thermal treatment. CeO2-MnO x -RO x (R = Al, La, Y, or Zr) mixed oxides were prepared by a co-precipitation method. The catalysts were characterized by XRD, BET, H2-TPR, CO chemisorption, XPS, TG analysis, soot–TPO, and NO–TPO. It is found that the introduction of R n+ into CeO2-MnO x markedly increases the thermal stability of the catalysts for soot and NO oxidation, remaining a better catalytic oxidation activity. On the one hand, after high-temperature aging, for the modified catalyst Pt/CeMnRO x , the ignition temperature of soot oxidation (T i) and maximal soot oxidation rate temperature (T m) increase by 30–50 °C and 4–32 °C, respectively, whereas Al3 +-modified catalyst shows the best thermal stability. On the other hand, due to a key role of NO2 as a strong oxidizing agent in soot oxidation process, the NO oxidation activity is often considered as an important aspect. This work shows that R n+-modified catalysts display a better stability on NO oxidation activity after aging. Some factors leading to the thermal deactivation of catalysts are also discussed in this paper.
Keywords: Soot oxidation; NO oxidation; Platinum; CeO2-MnO x mixed oxides; Thermal stability;

This paper investigates the potential use of ultrasonic treatment in comminution of coal in water media. A laboratory type, high intensity ultrasonic generator (750 W, 20 kHz) equipped with a horn transducer system and a titanium alloy horn tip (13 mm in diameter) was used as a source of ultrasonic treatment. The tests were performed at different levels of variables including ultrasonic power level (9.5–113.6 W/cm2), ultrasonic treatment times (5–20 min) and solid ratio of pulp (5–20% w/w). Temperatures of pulp atmosphere during ultrasonic treatment at different solid ratios and ultrasonic power levels were recorded. Particle size distribution curves were used to determine the degree of comminution. It was observed that ultrasonic treatment improved size reduction of coal significantly. Higher ultrasonic power levels and treatment times provided coal particles to be reduced to finer sizes. In addition, scanning electron microscope (SEM) and stereo microscope examinations were carried out to support test results. Selective comminuting ability of ultrasonic treatment was revealed from pyritic sulfur analysis for different size fractions of treated coal.
Keywords: Coal; Comminution; Ultrasonic treatment; Water media;

Development of value-added chemicals from glycerol, the co-product with biodiesel, is imperative in sustaining the biodiesel industry. Combined usage of a solid base and a copper-based catalyst provided a catalytic pathway to convert glycerol to racemic lactic acid. A new pathway was found that during the glycerol-to-lactic acid conversion, hydrogen was formed, which could be used in situ to generate propylene glycol catalyzed by the copper-based catalyst. This new pathway was attested by results of systematically experimental study investigating the synergistic functions of a base catalyst (CaO, MgO, or SrO) and a copper-based dehydrogenation catalyst (Cu, CuO, Cu2O, or Cu2Cr2O5). Different combinations of catalysts and reaction conditions provided a tunable range for the yield of lactic acid and propylene glycol. Emphasis was put on the combined use of CuO and CaO due to their inexpensive availability and ease of recyclability; at optimal reaction conditions, the yield of lactic acid reached 52 mol% together with 31 mol% yield of propylene glycol.Display Omitted
Keywords: Biodiesel; Glycerol; Calcium oxide; Copper-based catalysts; Lactic acid; Propylene glycol; Solid catalysts; Renewable chemicals;

A generalized model of SO2 emissions from large- and small-scale CFB boilers by artificial neural network approach by J. Krzywanski; T. Czakiert; A. Blaszczuk; R. Rajczyk; W. Muskala; W. Nowak (66-74).
Since the complexity of sulfur capture and release during solid fuel combustion in circulating fluidized bed (CFB) boilers, especially in the oxycombustion conditions is still not sufficiently recognized, the development of a simple SO2 emission model for wide range of operating conditions is of practical significance.The paper introduces the artificial neural network (ANN) approach for the prediction of SO2 emissions from CFB boilers. The model considers a wide range of parameters influencing SO2 emissions. The [16-1-6-1] ANN model was successfully applied to predict SO2 emissions from coal combustion in several large- and small-scale CFB boilers, over a wide range of operating conditions, both in air-firing as well as oxygen-enriched and oxycombustion conditions.Since the method constitutes a quick and easy to run technique this approach makes a complementary tool in relation to the experimental procedures and the programmed computing approach. Therefore, the model can be easily applied by scientists and engineers for simulations and optimizations of CFB units.
Keywords: Modeling; Circulating fluidized bed; Oxycombustion; SO2 emissions; Artificial neural networks;

Optimization of a log wood boiler through CFD simulation methods by Nesiadis Athanasios; Nikolopoulos Nikolaos; Margaritis Nikolaos; Grammelis Panagiotis; Emmanuel Kakaras (75-92).
This paper describes the steady-state modeling and simulation of a wood log fired boiler. It is designed and manufactured by THERMODYNAMIKI S.A. (KOMBI), a company based on Northern Greece. Its nominal fuel power is around 32 kW and its efficiency is close to 75%. A specific operating case, selected and experimentally investigated by the manufacturer, is examined. Due to the highly transient and complex nature of wood log combustion, an ad-hoc model has been developed. Its main characteristic is the fuel division into three components: water vapor, volatiles and fixed char. The latter is considered to form a layer, which is treated as a porous medium thus forming a volumetric source zone adjacent to the firebed area. Volatiles and water vapor are modeled as volumetric mass sources, whereas a two-step reaction mechanism of the former is considered. The numerical results are compared against corresponding experimental data for the nominal load as far as flue gas characteristics (temperature and species concentration) at the boiler exit, are concerned. Based on the validated model, a proposed optimization pattern of the boiler is undertaken and examined by means of CFD.
Keywords: Wood logs boiler; CFD; Boiler efficiency;

Slag viscosity as a function of temperature and composition is a very important factor in determining the operating temperature, blended coals as well as fluxing agents for slagging gasification. A number of models for predicting the viscosity of fuel slags have been developed, however, most of them are only valid in a limited range of temperatures and compositions. This study aims at developing a new viscosity model for fully liquid slag systems in the Newtonian range, based on the thermodynamic modified associate species model. The viscosity model is a structurally-based model, which gives a reliable prediction over the whole range of compositions and a broad range of temperatures. The focus of the present paper is to collect and model the experimental data for pure oxides SiO2, Al2O3, CaO, MgO, Na2O, K2O and binary systems SiO2–Al2O3, SiO2–CaO, SiO2–MgO, SiO2–Na2O, SiO2–K2O, Al2O3–CaO, Al2O3–MgO, Al2O3–Na2O, Al2O3–K2O, which is the first step to develop a new viscosity model for the system SiO2–Al2O3–CaO–MgO–Na2O–K2O. A good agreement between experimental data and calculated data has been achieved using only one set of model parameters, which have a clear physico-chemical meaning. Moreover, the extrapolated viscosities to the regions where no experimental data are available in literature are reasonable.
Keywords: Fuel slags; Viscosity; Thermodynamic modeling; Structure; Model; Gasification;

Effect of water on the separation of phenol from model oil with choline chloride via forming deep eutectic solvent by Shu-Hang Ren; Ying Xiao; Yi-Ming Wang; Jie Kong; Yu-Cui Hou; Wei-Ze Wu (104-108).
Choline chloride (ChCl) was demonstrated to efficiently separate phenols from model oils by forming deep eutectic solvents (DESs). The DES way is a non-aqueous process that avoids the use of mineral alkalis and acids, and prevents the production of wastewater containing phenol. However, real oils, such as coal tar oil and liquefaction oil, consist of a small amount of water, and ChCl is a strong hygroscopic compound, which may influence the removal of phenol in real oil. In this work, the effect of water in mixtures of phenol and toluene (defined as model oils) on the separation of phenol by forming DES with ChCl was studied. The results indicated that water could interact with ChCl to form DES and the interaction between water and ChCl was stronger than that between phenol and ChCl. In the presence of water in model oils, the amount of ChCl should be increased to get the same phenol removal as that without water. Moreover, with water in model oils, the influence of temperature on the phenol removal was more negative. After the reuse of ChCl for four cycles with the presence of water, ChCl accumulated about 23% water and the removal efficiency of phenol decreased from 92% to 87%. To reduce the effect of water on phenol separation, an air drying method could be used to remove water in regenerated ChCl.
Keywords: Phenol separation; Oil; Water; Choline chloride; Deep eutectic solvent;

Analysis of adsorption tests of gases emitted in the coal self-heating process by Agnieszka Dudzińska; Janusz Cygankiewicz (109-116).
The analysis of the results of sorption absorbency of hard coals with respect to gases relevant in assessing the fire hazard (carbon monoxide, carbon dioxide, hydrogen, ethylene, propylene, and acetylene) was the aim of this study. Hard coals adsorb carbon dioxide and acetylene in the highest amount, and ethylene and propylene in a slightly smaller amount. The adsorption of carbon monoxide and hydrogen is very small. The amounts of adsorbed gases depend on the metamorphism degree of hard coals as well as on their porosity. Hard coals of high porosity with good accessibility of internal surface, of low metamorphism degree and of higher oxygen content are characterized by greater adsorption capacity. Fire gases generated from the self-heating center may be the subject to adsorption on hard coals, which results in the lower gas concentration at the measuring points and as a consequence in the change of fire indicators calculated on their basis. This phenomenon applies in particular to hard coals with high sorption absorbency and to the situation in which the self-heating center and the point of measurement of concentrations is considerably distant, which causes greater contact of the emitted gas with coal matter, and more possible intensification of the adsorption process.Fire indicators are used to assess the development of the process of self-heating of coal. Gases, the concentration of which is the part of the particular fire indicator, should have a similar adsorption capacity. Indicators constructed on the basis of a very different adsorption capacity can be a source of errors due to the observed adsorption process.
Keywords: Coal; Coal self-heating; Adsorption; Unsaturated hydrocarbons;

Thermal treatments of two brown coals (Chinese and Australian brown coals) -slurries with four different aromatic solvents (hydrogen donor and non-donor, polar and non-polar solvents) were conducted with bench-scale apparatus, and the treated samples (TSs) were separated and characterized in detail to investigate the structural alterations of the coals, as well as the interactions between the solvents and the coals. It is observed that the thermal treatments in aromatic solvents are effective in upgrading the brown coals, but the reactivity of brown coals towards pyrolysis is reduced due to the extraction of small molecules and the enhancement of cross-linking reactions. The solvents are tightly combined with the brown coals owning to the formation of new chemical forces (such as hydrogen bonds or π–π conjugations) as well as the physical disruptions such as the collapse of pores during slurry-heating. Different solvents behave variously with their unique properties, especially tetrahydroquinoline (THQ), which is more tightly combined with the brown coals than the other solvents, including tetralin (THN), 1-methylnaphthalene (1-MN), recycle solvent (RS) due to the electron-affluent nitrogen atom on its aromatic ring. Hydrogen-donor solvent is superior to non-donor solvent for thermal treatment of brown coals.
Keywords: Brown coals; Aromatic solvents; Thermal treatments; Cross-linking;

Effect of hydrophobicity on viscosity of carbonaceous solid–water slurry by Amrita Mukherjee; Peter Rozelle; Sarma V. Pisupati (124-130).
Carbonaceous solid–water slurry rheology is greatly affected by the surface properties of the carbonaceous solids used. Slurriability studies showed that, for the same solids loading, viscosities of highly hydrophobic petcoke and bitumen–water slurries were approximately one order of magnitude higher than the viscosity of non-hydrophobic Illinois #6 (bituminous) coal–water slurry. Apart from slurriability, the hydrophobicity of the carbonaceous solids was found to influence the type of additives used to reduce the viscosity. Selected to reduce viscosity, the addition of non-ionic additive Triton X-405 caused a drastic reduction in petcoke and bitumen–water slurry viscosities, whereas anionic additive ammonium lignosulfonate reduced Illinois #6 coal–water mixture viscosity more effectively. Optimum particle-size distribution was also found to be dependent on the surface properties of the solids. Experimentally determined optimum particle-size distributions were observed to deviate from the theoretical predictions. A deviation of 8% was noted in the case of Illinois #6 coal–water slurry, whereas deviations of 30% were observed in the case of hydrophobic bitumen and petcoke–water slurries. Viscosity predictions of semi-empirical models were compared to experimentally measured viscosities. The predicted viscosities did not match the experimental results, especially at higher solids loading. A thixotropic model taking into account particle aggregation was found to predict viscosity more accurately in the case of these hydrophobic carbonaceous solid–water slurries.
Keywords: Coal; Petcoke; Hydrophobicity; Aggregation; Optimum particle-size distribution; Viscosity;

This study evaluated the applicability of the distributed activation energy model (DAEM) while incorporated in a particle model designed for entrained flow pyrolysis of biomass. For that purpose, two types of biomass (spruce sawdust and coconut shell) were pyrolyzed in a thermogravimetric analyzer to obtain the intrinsic kinetic parameters. These kinetic parameters were then incorporated in the particle model. For comparison, entrained flow pyrolysis of those samples was also conducted at different temperatures (1073 and 1273 K) by varying particle size (150–250 μm and 500–600 μm). The modeling results were also compared with the literature data. The prediction using DAEM kinetics was improved when pyrolysis heat of reaction was included in the model. Based on the findings, a method was proposed to use the intrinsic kinetic parameters for particle simulation to determine the conversion profile of biomass pyrolysis under laminar entrained flow condition.
Keywords: Particle simulation; DAEM; Pyrolysis; Biomass; Entrained flow;

Activated carbons from waste biomass and low rank coals as catalyst supports for hydrogen production by methanol decomposition by B. Tsyntsarski; I. Stoycheva; T. Tsoncheva; I. Genova; M. Dimitrov; B. Petrova; D. Paneva; Z. Cherkezova-Zheleva; T. Budinova; H. Kolev; A. Gomis-Berenguer; C.O. Ania; I. Mitov; N. Petrov (139-147).
Activated carbons with different textural and chemical surface characteristics were synthesized from waste biomass and low rank coals, and furthermore used as a host matrix for cobalt species, varying the preparation and modification methods. The obtained activated carbons and modified samples were characterized by complex of various physicochemical methods, such as: low temperature physisorption of nitrogen, XRD, EPR, XPS, UV–Vis and TPR with hydrogen. Boehm method was applied for qualitative and quantitative determination of oxygen-containing groups on the carbon surface before and after cobalt deposition. The catalytic properties of cobalt modifications were tested in methanol decomposition. The dominant effect of activated carbon texture over the surface chemistry on the state and catalytic behavior of cobalt species was discussed.
Keywords: Activated carbon; Waste biomass; Coal tar pitch; Cobalt modification; Methanol decomposition; Hydrogen;

Short term online corrosion measurements in biomass fired boilers. Part 1: Application of a newly developed mass loss probe by Stefan Retschitzegger; Thomas Gruber; Thomas Brunner; Ingwald Obernberger (148-156).
Online corrosion probes enable the online determination of high-temperature corrosion rates in biomass combustion plants. These probes are exposed to the flue gas and require a layer of corrosion products and deposits on their surface to be able to perform the corrosion measurements. The formation of this layer takes time and depends on the build-up rate of the deposits as well as on the ability of the deposits to form a conductive layer. During this initial phase, which lasts about 300 h based on experiences with forest wood chip combustion, the measurements are inaccurate. This inaccuracy can be neglected during long-term measurements performed at real-scale plants which last more than several 1000 h. Since high-temperature corrosion in biomass combustion plants is known to generally follow a paralinear trend, high corrosion rates prevail in the beginning. Following, if short-term measurements shall reflect or come close to real-life conditions, this “start-up” effect cannot be neglected.Consequently, to be able to correct this “start-up” effect, a methodology has been developed which combines results from parallel measurements of an online corrosion probe and a mass loss probe. The mass loss probe consists of multiple test rings and is exposed to the flue gas next to the corrosion probe with similar surface temperatures. With the mass loss probe the trend of the corrosion rate within the first 300 h is determined by gravimetric mass loss measurements of each ring. For evaluation this trend of the corrosion rate from the mass loss probe is coupled with the signal from the corrosion probe. Hereby, the inaccuracy at the beginning of the online corrosion probe measurements can be eliminated and reliable short-term measurements can be performed. A 50 kW biomass grate combustion system coupled with a drop tube was used for the development of the mass loss probe and the evaluation methodology. Such a test rig provides multiple advantages for high-temperature corrosion measurements compared to a real-scale plant. Specific and homogenous fuels can be tested, specific influencing parameters can be adjusted and varying operating conditions occurring in a real-scale plant are excluded.
Keywords: Biomass combustion; High-temperature corrosion; Online corrosion measurements;

A novel extractive gas-phase sampling system was developed for use in a pressurized entrained-flow coal gasifier. The system comprised three parts: a water-cooled probe through which the sampled gases travel, a pneumatic cylinder that directs the radial sampling location, and the control system. The system was designed for safe sampling of the harsh environment in gasifiers and can help understand spatial distribution of concentrations in such a system. To confirm operation of the sampling system, gas-phase samples were extracted from the reaction zone of a 1 ton/day pilot entrained-flow coal gasifier operating at a pressure of 11 bar and at temperatures ranging from 1370 to 1540 °C. Concentrations of carbon monoxide and hydrogen decreased with increasing temperature while carbon dioxide increased with temperature, a result of the higher oxygen/fuel ratio needed to achieve the higher temperature. Synthesis gas (syngas) heating values decreased correspondingly with increasing temperature and the heating value of the syngas exiting the gasifier was higher than for syngas extracted from the reaction zone. Under conditions tested, no statistically significant variation in gas composition with radial position was observed.
Keywords: Gasification; Coal; Pressurized; Entrained-flow; Sampling; Gas-phase;

Uranium oxide-supported gold catalyst for water–gas shift reaction by Yuan-Yuan Dong; Wei-Ping Liao; Zhang-Huai Suo (164-169).
The orange yellow UO3 and bottle green U3O8 phases were prepared by thermal decomposition of uranyl nitrate hexahydrate at 400 °C and 500 °C, respectively. Gold catalysts supported on two oxides were prepared by incipient wetness impregnation for water–gas shift reaction. The gold catalysts were characterized by the techniques such as nitrogen physical adsorption, X-ray diffraction, temperature-programmed reduction, and X-ray photoelectron spectroscopy. The Au/UO3 catalyst has both microporous and mesoporous structures while the Au/U3O8 catalyst has only microporous structure. The presence of gold on the oxide surface greatly facilitates the reduction of uranium oxide support. The active sites for water–gas shift reaction are likely dominant metallic gold with a small portion of oxidized gold species due to UO2 +/U4 + redox property. The Au/UO3 catalyst shows higher activity with 55% conversion of CO in comparison with Au/U3O8. High activity on Au/UO3 catalyst is attributed to facile the reducibility of UO3 and its high surface gold atomic concentration.
Keywords: Uranium oxide; Gold catalyst; Water–gas shift reaction; Activity; Structure characterization;

Pyrolysis of spent coffee grounds using a screw-conveyor reactor by Shantanu Kelkar; Christopher M. Saffron; Li Chai; Jonathan Bovee; Thomas R. Stuecken; Mahlet Garedew; Zhenglong Li; Robert M. Kriegel (170-178).
The fast pyrolysis of spent coffee grounds using a compact, transportable, screw conveyor reactor for producing bio-oil was studied. A two-factor, five-level, central composite response surface experiment was completed to formulate a statistical model that relates reactor temperature (429–550 °C) and residence time (23–42 s, controlled by the screw rotation rate) to bio-oil yield and quality. Regression analysis of model fits with experimental data showed that temperature and residence time had a significant effect (p  < 0.05) on bio-oil yield. Highest bio-oil yield (61.8%) was observed at 500 °C while the highest char yield (20.6 % w/w) was produced at the lowest temperature of 429 °C. Bio-oil yields increased with screw speed and decreasing residence time. The model predicted a maximum liquid yield of 61.7% and an accompanying char yield of 17.1% at 505 °C (778 K) and 70 rpm. In addition to containing oxygenated organic compounds typical of bio-oils, spent coffee bio-oil also contains more hydrophobic compounds (> 20% peak area) such as fatty acids, fatty acid esters, medium-chain paraffins, olefins, and caffeine. Because of the abundance of spent coffee grounds and the quality of its bio-oil, this waste stream offers potential as a valuable bioenergy feedstock.
Keywords: Pyrolysis; Bioenergy; Bio-oil; Coffee; Screw-conveyor reactor;

CO2 chemical absorption in 3-amino-1-propanol aqueous solutions in BC reactor by Jessica Bentes; Alicia García-Abuín; Allen G. Gomes; Diego Gómez-Díaz; José M. Navaza; Antonio Rumbo (179-185).
The present paper analyzes the overall carbon dioxide absorption process in aqueous solutions of 3-amino-1-propanol using a bubble column reactor (BCR). These studies focus on the absorption rate, the reactor hydrodynamics, the speciation during the experiments, the changes in liquid phase temperature and the solvent regeneration to be used in new absorption cycles. Some of these studies have allowed knowing the importance of each involved reaction in the mechanism, while others allow evaluating the potential use of this amine for carbon dioxide capture in an industrial process.Display Omitted
Keywords: Carbon dioxide; Absorption; Amine; Regeneration; NMR;

A two-step biodiesel production process from waste cooking oil via recycling crude glycerol esterification catalyzed by alkali catalyst by Zi-Zhe Cai; Yong Wang; Ying-Lai Teng; Ka-Man Chong; Jia-Wei Wang; Jie-Wen Zhang; De-Po Yang (186-193).
A novel biodiesel production process using waste cooking oil (WCO) as feedstock was developed in this work. Free fatty acids (FFAs) from WCO were esterified by crude glycerol catalyzed by NaOH, which lowered the content of free fatty acids of WCO. The conversion of FFA in the WCO (acid value: 124.9 mg KOH/g) to acylglycerols is 99.6% under the optimal conditions (1.4:1 molar ratio of glycerol to FFA, 4 h, 210 °C, catalyst loading 0.5 wt.% based on WCO weight). After the transesterification of esterified WCO with methanol catalyzed by NaOH, the yield of the final product is 93.1 wt.% with 98.6 wt.% of fatty acid methyl ester (FAME). The crude glycerol and the catalyst from transesterification were recycled as reactant for esterification during the biodiesel production. Soap formed from the subsequent processes maintained a high catalyzing activity for FFA esterification after being recycled for 13 times. This new glycerol esterification process using alkali (soap) catalyst provides a promising solution to convert feedstock with high FFA levels to biodiesel. This biodiesel production process has distinct advantages compared with traditional two-step methods, including lower cost of catalyst for both esterification and transesterification processes, less energy consumption for methanol recovery, recycling of the glycerol byproduct and catalyst (soap), and no requirement of anti-corrosive equipment.
Keywords: Biodiesel; Waste cooking oil; Alkali catalyst; Crude glycerol; Esterification;

Mathematical model of the water sorption kinetics of UBC by Takuo Shigehisa; Toshinori Inoue; Haruo Kumagai (194-203).
The water sorption kinetics of UBC (Upgraded Brown Coal) and its feedstock coals, including raw and dried coals, were investigated. A pseudo 1st order model was suitable for the desorption of raw coal, and a pseudo 2nd order and Elovich model was determined for both sorptions of the UBC and dried coal. This finding corresponded with the fact that the water adsorption status of the surface of the coal was modified through drying. The finding also indicated that the water sorption by the UBC and dried coal can be explained by similar kinetic models. These models were empirical, and the constants of the equations were determined from existing data. Therefore, the models cannot predict the sorption rate for given environmental conditions, such as temperature, relative humidity and initial moisture. To solve this problem, the Elovich model was converted by variable transformation to include the equilibrium moisture. The constants of the converted model could be determined for any given condition. The converted-Elovich model resembled the Langmuir model with regards to the driving force, although the force acted in a non-linear way, which was unlike the original Langmuir model. The reason why the constants could be determined was explained through this resemblance. Therefore, the converted-Elovich model was demonstrated to be effective not only in the fitting of existing data but also in the estimation of the sorption rate for any given conditions. The model was close to theoretical.Display Omitted
Keywords: Low rank coal; UBC; Water sorption kinetics; Elovich model; Pseudo 2nd order model; Langmuir model;

Methanation of carbon dioxide over Ni–M/ZrO2 (M = Fe, Co, Cu) catalysts: Effect of addition of a second metal by Jun Ren; Xiang Qin; Jin-Zhou Yang; Zhi-Feng Qin; Hai-Long Guo; Jian-Ying Lin; Zhong Li (204-211).
Ni/ZrO2 catalysts with an added second metal were prepared by impregnation method and used in CO2 methanation. X-ray diffraction, hydrogen temperature programmed reduction, hydrogen temperature programmed desorption, X-ray photoelectron spectroscopy, and in situ infrared spectroscopy measurements were taken to characterize the surface and bulk properties of the catalysts. Compared with Co and Cu, Fe could efficiently enhance the catalytic activity of Ni/ZrO2 in CO2 methanation at low temperatures. The optimal amount of Fe was 3 wt.%. CO2 methanation over Ni–Fe/ZrO2 catalysts may proceed through dissociation of CO2 into CO and subsequent reaction of CO with hydrogen to generate methane. Addition of Fe not only can improve the dispersion and degree of reduction of Ni, but also can enhance the partial reduction of zirconia. These effects further promote adsorption and dissociation of H2 and CO2, thus enhancing the activity of the catalyst in CO2 methanation.Display Omitted
Keywords: Bimetallic catalyst; CO2 methanation; ZrO2 support; Low-temperature activity;

Biomass-derived sugars and furans: Which polymerize more during their hydrolysis? by Xun Hu; Sri Kadarwati; Shuai Wang; Yao Song; M.D. Mahmudul Hasan; Chun-Zhu Li (212-219).
Sugars and furans are important intermediates during the conversion of non-food lignocellulosic biomass to biofuels and chemicals. In this study, polymerization of the sugars (glucose, fructose, xylose) and furans (5-hydroxymethylfurfural, furfural) during their acid-catalyzed conversion was investigated. The potential cross-polymerization between sugars and furans was explored. Sugars and furans have very different tendencies towards polymerization. Yields of solid polymer (weight basis) during the dehydration of glucose to 5-hydroxymethylfurfural (HMF) is ca. 7% while that from HMF to levulinic acid is ca. 17% at 190 °C with Amberlyst 70 as the catalyst. Dehydration of xylose to furfural forms negligible amounts of solid polymer, while furfural polymerized almost completely. Cross-polymerization between HMF and glucose is insignificant. However, HMF does cross-polymerize with fructose and furfural, producing more insoluble polymer and soluble polymers with different structures. The cross-polymerization between furfural and xylose, if any, does not have any appreciable impact on formation of the insoluble polymer or soluble polymer. Efforts should be devoted more to stabilize the furans to diminish their polymerization during acid-catalyzed conversion of biomass/sugars/furans to value-added chemicals or biofuels.In acidic environment, both the biomass derived sugars and the furans can polymerize and cross-polymerize as well. Is this true?Display Omitted
Keywords: Acid-catalyzed conversion; Glucose and xylose; Furfural and HMF; Polymerization; Levulinic acid;

γ-Alumina and carbon supported mono and bimetallic Ni and Cu catalysts were synthesized and applied to the reduction of p-cresol and furfural via transfer hydrogenation. The developed reaction system was applied to alkyl phenol rich pyrolysis oils produced from the ARS tail gas reactive pyrolysis (TGRP) of switchgrass and oak wood. The catalysts used were characterized pre- and post-reactions using XRD, TPR, TEM and TGA. When isopropanol was used as the hydrogen donor solvent, yields of > 95% of a mixture of products from the reduction of p-cresol were achieved using the Ni–Cu/Al2O3 catalyst. This product mixture includes ring hydrogenation products (4-methylcyclohexanol and 4-methylcyclohexanone) as well as deoxygenated products (methylcyclohexane and toluene), with 4-methylcyclohexanol being the major product. The activity remained high in the presence of water with very high levels of water concentration resulting in a higher selectivity towards the ketone product. The system was also effective for the reduction of furfural to furfuryl alcohol, although lower temperatures were required to prevent polymerization of the furfural. When applied to bio-oil, although increases in H/C and C/O ratios and energy content were realized, effective reduction of the alkyl phenols in the bio-oils was below expectation. Rather, solid formation, a result of the polymerization of bio-oil compounds was also observed. Our effort to extend the successes encountered with the model compounds to improve the application of transfer hydrogenation to real bio-oils is the subject of ongoing research.
Keywords: Transfer hydrogenation; p-Cresol; Bio-oil; Catalysis;

Upgrading of chlorinated oils coming from pyrolysis of plastic waste by A. Lopez-Urionabarrenechea; I. de Marco; B.M. Caballero; M.F. Laresgoiti; A. Adrados (229-239).
The objective of this paper is the upgrading of chlorinated oils coming from the pyrolysis of mixed plastic waste, in order to use them as fuel or feedstock for refineries. Two different samples of pyrolysis oils have been thermally and catalytically cracked in a 300 mL autoclave at 325 °C and the auto-generated pressure. Thermal cracking converts the plastic pyrolysis heavy oils into light liquid fractions which are only composed of alkanes and aromatics. These light fractions present a very low quantity of chlorine compared to the initial oils and resemble gasoline and diesel-like products. Besides, a gaseous fraction rich in methane and with very high heating value is also produced, together with a fuel-like viscous product which remains in the autoclave. The relative proportions of each of these three fractions depend on the nature of the initial oils. Red Mud has proved to be a dehydrochlorination and cracking catalyst, since it gives rise to higher quantity of gases and light liquid fractions with a very low chlorine content (< 0.1 wt.%). Therefore, dechlorinated light oils can be obtained by Red Mud low temperature catalytic cracking of plastic derived chlorinated pyrolysis oils.
Keywords: Pyrolysis oils; Upgrading; Thermal cracking; Catalytic cracking; Dechlorination; Plastic waste;

This study reports the characterization and the leaching behaviors of three fly ashes taken from different low grade-lignite-fired stations. Fly ashes were characterized in terms of their physical, chemical, mineralogical and morphological properties. Leaching behaviors of these ashes were studied by means of two standard leaching tests, namely TCLP and ASTM D3987. In this context, both the eluates and solid residues of these tests were investigated. Some selected major, minor and trace element (Ag, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Sb, Se, Sr, Ti, Zn) concentrations were analyzed in the leaching eluates. Calcium was a major cation having the highest extraction ratio in all samples regardless of the leaching test used. On the other hand, in ASTM tests, the extraction ratios are higher than 0.1% for selected elements (except Mg, Zn) whereas in TCLP tests, they are higher than 1% for the majority of selected elements. Solid residues were also analyzed to determine the mineralogical and morphological transformations during the leaching process. While lime and anhydrite were consumed in Yatagan fly ash (YFA) and Soma fly ash (SFA), secondary phases such as ettringite and/or calcium silicate hydrates precipitated in their solid residues; however, similar transformations could not be observed in Seyitomer fly ash (SoFA). Therefore, YFA and especially SFA can be accepted as inert wastes due to the ettringite formation. Since ettringite stabilizes several toxic elements such as As, Cr, Se and Sb by incorporating them to its structure.
Keywords: Fly ash; Trace element; Leaching tests; Leach residue; Ettringite;

Experimental and kinetic investigation of the plasma catalytic dry reforming of methane over perovskite LaNiO3 nanoparticles by Xiao-Gang Zheng; Shi-Yu Tan; Li-Chun Dong; Shao-Bo Li; Hong-Mei Chen; Shun-An Wei (250-258).
Plasma-assisted catalytic conversion of CH4 and CO2 into synthesis gas was performed in a dielectric barrier discharge reactor coupled with perovskite La–Ni nanoparticles (LaNiO3 NPs). Compared to supported catalysts such as Ni/γ-Al2O3, La–Ni/γ-Al2O3 and Ni/La2O3, LaNiO3 NPs showed better catalytic performance. The results show that the low flow rate of feed gases and high input power were favorable for the conversions of CH4 and CO2 as well as the selectivities of desired products, but led to lower energy efficiency. A global kinetic model according to argon dilution in plasma-catalytic system was proposed and employed to foresee the CH4 and CO2 conversion assisted by plasma-catalysts hybrid effect. The kinetic model indicates that the reactant conversion rate was an exponential function of the discharge energy.
Keywords: Kinetic model; LaNiO3; Dry reforming of methane; Dielectric barrier discharge;

Reforming of tars and organic sulphur compounds in a plasma-assisted process for waste gasification by Massimiliano Materazzi; Paola Lettieri; Luca Mazzei; Richard Taylor; Chris Chapman (259-268).
Waste gasification is considered a valuable and sustainable solution to the production of clean energy (via gas turbines or gas engines) and bio-fuels, such as synthetic natural gas and bio-hydrogen, provided that the syngas produced in the gasifier is free of condensable tars and organic sulphur contaminants that cause equipment fouling and deactivation of catalytic stages downstream. In particular, catalytic reaction stages are highly sensitive to specific trace contaminants (e.g. PAHs, thiophenes, etc.), necessitating the use of additional cleaning operations to remove these residues to levels where the catalyst degradation is acceptable. In this work, the use of thermal plasma (coupled with primary waste treatment) to completely reform tars and organic sulphur compounds to simple gaseous products (predominantly H2 and CO) is assessed. To this end, a 20-hour waste gasification run was performed on a two-stage fluid bed-plasma demonstration plant to investigate the tar evolution in the syngas, with special attention on the chemistry of generic and sulphur-substituted aromatics within the plasma stage. The organic fraction in the gas phase was found to be completely reformed under plasma conditions, leaving essentially CO, H2 and H2S as ultimate products. In particular, reduction efficiencies typically exceeded 96%v/v for complex organics (e.g. PAH) and thiophenes were observed. The syngas, after a tertiary simplified gas cleaning process, is suitable for high efficiency power generation, or conversion to a fuel gas capable of injection into national or industrial supply grids.
Keywords: Waste gasification; Fluidized bed; Plasma; Tar; Sulphur;

In Europe and Japan, benzene, toluene, and xylenes (BTX) are usually obtained by liquid–liquid extraction from pyrolysis gasolines using organic solvents such as sulfolane. In the last few years, ionic liquids (ILs) have been studied as potential substitutes of conventional solvents in the extraction of BTX from alkanes. In this paper, we have studied the dearomatization of pyrolysis gasolines obtained by mild and severe cracking using the binary IL mixture composed of the 1-ethyl-4-methylpyridinium bis(trifluoromethylsulfonyl)imide ([4empy][Tf2N]) and the 1-ethyl-3-methylimidazolium dicyanamide ([emim][DCA]) and also employing sulfolane to compare the performance of both extraction solvents. To choose the most appropriate conditions of temperature and solvent to feed ratio to perform the extraction of BTX from pyrolysis gasolines, several extractive properties have been estimated from the experimental results employing the IL mixture and sulfolane. Simulations of countercurrent extraction columns in the dearomatization of both pyrolysis gasolines have also been made using the Kremser equation. The dearomatization of pyrolysis gasolines by the {[4empy][Tf2N] + [emim][DCA]} IL mixture would require a higher number of equilibrium stages in the extractor than that employing sulfolane. By contrast, the purity of extracted aromatics would be substantially greater using the IL-based solvent, simplifying the subsequent purification of the BTX.
Keywords: Liquid–liquid extraction; Dearomatization; Ionic liquids; Pyrolysis gasoline; Simulation of a countercurrent column;

Performance of a conical spouted bed pilot plant for bio-oil production by poplar flash pyrolysis by Jon Makibar; A. Ruth Fernandez-Akarregi; Maider Amutio; Gartzen Lopez; Martin Olazar (283-289).
Poplar (Populus nigra) flash pyrolysis has been performed at the IK4-Ikerlan 25 kg h− 1 pilot plant equipped with a conical spouted bed reactor. Gas, bio-oil and char yields and properties have been studied in the 425–525 °C range. This reactor has been proven to be especially suitable for this process as high bio-oil yields have been obtained, with the maximum being 69 wt.% at 455 °C. The bio-oil has been collected in two fractions: the lighter one, which accounts for 85 wt.% of the bio-oil, has a high water content and is composed mainly of acids and ketones, whereas the heavier fraction has a lower water content and is rich in phenols. These fractions are miscible, obtaining a bio-oil with a water content lower than 25 wt.% and a higher heating value in the 16–18 MJ kg− 1 range.
Keywords: Spouted bed; Flash pyrolysis; Biomass; Bio-oil; Scale up; Poplar;

Tuning of product selectivity in the conversion of ethanol to hydrocarbons over H-ZSM-5 based zeolite catalysts by Thanh Khoa Phung; Randy Radikapratama; Gabriella Garbarino; Alberto Lagazzo; Paola Riani; Guido Busca (290-297).
Conversion of ethanol to hydrocarbons was investigated over H-ZSM-5 zeolite and its modification by addition of phosphorus, iron and nickel. Reaction is realized in a tubular flow reactor at atmospheric pressure. Catalyst characterization was performed by UV–vis, TG–DTA, XRD, NH3-TPD, and IR spectroscopy of the surface OH groups and of adsorbed pyridine. High P content enhances the selectivity to lower olefins, in particular ethylene, as also occurs in the case of Fe addition. Over Ni-modified zeolites, C4 and aromatic production is promoted. The role of acidity on the conversion path is briefly discussed.Display Omitted
Keywords: H-ZSM-5; Ethanol; Phosphorus; Aromatics; Olefins; NH3-TPD;

Industrialization of enzyme-catalyzed biodiesel production has been hindered by low conversion efficiency and long reaction time. As a representative example, Rhizopus oryzae lipase (ROL) exhibited a poor performance in biodiesel production. However, higher yields and shorter reaction time could be achieved by screening different lipases that could synergically catalyze the reaction with ROL. The results showed that Novozym 435 combined with ROL displayed the best performance, with a biodiesel yield that was 30% higher than that of ROL alone in 30 h. Hence, the use of a synergic strategy was investigated systematically. Under optimized conditions, the biodiesel yield was as high as 98.3% and the reaction time was successfully shortened from 60 h to 21 h. Moreover, the combined lipases retained a yield of about 80% after 20 cycles in a solvent-free system. In addition to ROL, the performance of other lipases whose regioselectivity were similar to ROL was improved when they were combined with Novozym 435. In conclusion, synergic catalysis is a promising strategy for enhancing biodiesel yield and minimizing reaction time for ROL.
Keywords: Biodiesel yield; Novozym 435; Reaction time; Rhizopus oryzae lipase; Synergic effect;

Molecular structure and size of asphaltene and preasphaltene from direct coal liquefaction by Zhi-Cai Wang; Yan Ge; Heng-Fu Shui; Shi-Biao Ren; Chun-Xiu Pan; Shi-Gang Kang; Zhi-Ping Lei; Zhi-Jun Zhao; Jing-Chen Hu (305-311).
The heavy organic components in the direct coal liquefaction residue (DCLR), such as asphaltene (AS) and preasphaltene (PA) have significant influence on the direct coal liquefaction (DCL) technology. In this paper, the molecular structure and size of two types of AS and PA from the DCLR of 6 t/d Shenhua process developing unit and a batch hydro-liquefaction in laboratory were characterized. Results indicated that two types of AS and PA from different liquefaction technologies respectively display similar distribution of fluorophors. 3 ~ 4 rings fused aromatic nucleus (ANs) and/or more rings peri-condensed ANs are the predominating structures in the AS and PA. The scale of PA molecule is significantly larger than that of AS molecule. The molecular model, in which several ANs linked by bridge bonds or hydrogenated aromatic rings, is valid at least for the PA. Both AS and PA from direct coal liquefaction can form aggregates while the PA exhibits stronger aggregation than the AS.
Keywords: Liquefaction residue; Asphaltene; Preasphaltene; Molecular size; Aggregation;

Co-firing of coal with biomass suffers from high thermal reactivity of biomass. Thus, this paper discusses the effectiveness of carbonization to reduce the excess reactivity of biomass to avoid segregation of coal and biomass during co-firing. In this context, Robinia pseudoacacia (RP) that is a promising woody biomass has been subjected to carbonization at 600 °C to obtain a biochar that has relatively lower reactivity. Fuel properties and thermal analysis profiles (TGA, DTG, DSC) of biochar were compared with those of biomass and lignite to valorize the effectiveness of carbonization. Segregation of biomass and lignite during co-combustion before and after carbonization was investigated considering 50/50 wt% blends. It was concluded that carbonization based co-firing of biomass with lignite mostly eliminates segregation tendency in the mass loss characteristics as well as the heat flow pattern due to the change in the burning mechanism that leads overlapping the temperatures of maximum rate of weight loss (TR-max) and maximum heat flows (TH-max). The carbonization process allows co-utilization with high substitution ratios of biomass. Carbonization based co-firing of biomass and lignite also showed that the heat flow pattern does not suit to additive behavior, while the weight loss characteristics are partly additive and partly non-additive depending on the temperature interval.
Keywords: Co-firing; Carbonization; Segregation; Robinia pseudoacacia; Lignite; Additivity;

Experimental determination of effective moisture diffusivity during the drying of clean olive stone: Dependence of temperature, moisture content and sample thickness by Francisco J. Gómez-de la Cruz; José M. Palomar-Carnicero; Pedro J. Casanova-Peláez; Fernando Cruz-Peragón (320-326).
Drying of clean olive stone (free of olive pulp) means a revaluation as biofuel especially used for thermal processes. This work has studied the time-dependent effective moisture diffusivity from isothermal drying experiments in a convective dryer. A new method, based on a modification of the simplified method, has been established to calculate this coefficient. A comparison between this method and the slope method has been carried out and similar results have been obtained. Modified simplified method requires fewer calculations than the slope method. The dependence between the effective moisture diffusivity, the temperature and the moisture ratio was analyzed by multiple regression analysis from a second order multivariate polynomial model and the mechanisms of moisture transport were exposed. Finally, the activation energy was analyzed and its values were shown with respect to the moisture ratio and the sample thickness.Display Omitted
Keywords: Olive stone; Biomass; Drying; Effective moisture diffusivity; Mathematical modeling;

A study of smoke formation from wood combustion by A.R. Lea-Langton; M.T. Baeza-Romero; G.V. Boman; B. Brooks; A.J.M. Wilson; F. Atika; K.D. Bartle; J.M. Jones; A. Williams (327-332).
Aerosol time of flight mass spectrometry (ATOFMS) was used to analyse the particles emitted during the flaming and smouldering phases of the combustion of samples of hard and soft woods. Eugenol and furfural were also burned and using results from previous work of the authors, they have been shown to be useful proxies for initial wood combustion products. The ratios of elementary carbon to total carbon in the particles were similar for both the woods and for eugenol. The ATOFMS spectra of most of the particles were consistent with the presence of soot precursor constituents along with oxygen containing fragments. Most particle diameters were less than 2.5 μm, with the greatest concentration of < 0.12 μm.
Keywords: Wood; Combustion; Particulate matter;

The hydrophobic flocculation of the lignite obtained from the Ermenek region was investigated under the different operating parameters such as pH, sodium silicate concentration and kerosene concentration in the present work. Determination of combustible recovery, ash content and zeta potential values were utilized in order to make sense of the hydrophobic flocculation behavior. To specify indirectly the hydrophobicity degree of the coal, contact angle measurements were performed on the flocks obtained from the experiments.The combustion characteristics of coal such as thermogravimetric analysis (TGA) and differential thermogravimetric analysis (DTGA), ignition temperature, and peak temperature were analyzed and correlated with the hydrophobic flocculation.In consequence, optimum pH value was determined as to be 4; optimum sodium silicate and kerosene concentration were also ascertained as to be 1 kg/t and 16 kg/t, respectively. When experimental conditions were set up optimally, the flocks were obtained with combustible recovery of 90% and ash content of 9.8%. The strong correlation was observed between the hydrophobic flocculation results and ignition temperatures and peak temperatures acquired from the DTGA curves. The surface tension of solution, however, showed no remarkable changing. It was confirmed that the contact angle values ranged from 114° to 130° and the surfaces were highly hydrophobic.Display Omitted
Keywords: Coal; Hydrophobic flocculation; Contact angle; TGA; DTGA;

The effect of tetrahydrofuran on the base-catalyzed sunflower oil methanolysis in a continuous reciprocating plate reactor by Ivana B. Banković-Ilić; Zoran B. Todorović; Jelena M. Avramović; Ana V. Veličković; Vlada B. Veljković (339-350).
The homogeneous base-catalyzed methanolysis of sunflower oil in the presence and absence of tetrahydrofuran (THF) as a co-solvent was studied in a continuous cocurrent upflow reciprocating plate reactor (RPR). The measurements of the dispersed phase drop size demonstrated the effects of the THF concentration on the Sauter-mean drop diameter and the drop size distribution in both non-reactive (methanol/oil) and reactive (methanol/KOH/oil) systems. The presence of THF shifted both heterogeneous systems to the stable homogeneous emulsion consisted of small dispersed phase drops. The triacylglycerol (TAG) conversion degree was measured in the reactive system. The sigmoidal kinetics was observed in the absence and presence of THF at lower THF concentrations (≤ 10% of the oil mass). This shape was explained by the existence of the initial TAG mass transfer controlled region followed by the irreversible second-order reaction controlled region. However, at the highest THF concentration (30% of the oil mass) the irreversible and reversible second-order reaction kinetics was used to describe the variation of TAG conversion degree with time. The proposed kinetic models satisfactorily fitted the experimental data.
Keywords: Biodiesel; Continuous process; Drop size; Kinetics; Modeling; Reciprocating plate reactor; Tetrahydrofuran;

Coal and plastic waste co-pyrolysis by thermal analysis–mass spectrometry by S. Melendi-Espina; R. Alvarez; M.A. Diez; M.D. Casal (351-358).
Simultaneous thermogravimetry–mass spectrometry studies of a pyrolytic decomposition of mixtures of different plastic wastes/coking coal were carried out. The investigation was performed at temperatures up to 1000 °C in a helium atmosphere under dynamic conditions at a heating rate of 25 °C/min. Five thermoplastics, commonly found in municipal wastes: low density polyethylene (LDPE), high density polyethylene (HDPE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET) and a plastic mixture rich in polyolefins were selected. Thermogravimetric parameters, together with different characteristic ion fragments from selected libraries of evolving products during the co-pyrolysis process were monitored, such as hydrogen, CO2 and aliphatic and aromatic hydrocarbons. Based on the results obtained, a synergistic effect between coal and individual residues has been found. The maximum interaction occurs at temperatures close to the maximum release of volatile matter of the plastic waste. There is a delay in the decomposition of the plastics that together with the changes in the composition of the volatile matter evolved, promote interactions between the components and have negative effects on coal fluidity. The polyolefinic wastes (HDPE, LDPE and PP) degrade at temperatures close to that of maximum coal degradation, modifying the thermal behaviour of the coal to a lesser degree. However, PS and PET, that release their volatile matter mostly in the early stage of the coal decomposition, show a more pronounced influence on the thermal behaviour. Moreover, the kinetic data demonstrates that the addition of polyolefins increases the energy required to initiate pyrolysis compared to PS and PET. All of these results agree with the fact that polyolefins reduce coal fluidity in a more moderate way than PET and PS.
Keywords: Coal; Plastic wastes; Co-pyrolysis; TG-MS; Evolved gas;

Comparison of various post-treatments for recovering methane from agricultural digestate by C. Sambusiti; F. Monlau; E. Ficara; A. Musatti; M. Rollini; A. Barakat; F. Malpei (359-365).
At full scale biogas plants, a large amount of digestate, which still contains a residual methane potential, is produced daily. Problems related to digestate storage and its use (i.e., biogas losses, the high cost of digestate transportation and limitations imposed by the European Nitrate Directive on its use as soil amendment) have attracted great attention among researcher to find solutions to take advantage of its residual methane potential. Thus, the aim of this study was to evaluate the methane production from digestate (DIG) and solid separated digestate (SS-DIG) and the feasibility of applying different kinds of post-treatments (i.e., thermal, thermo-chemical and enzymatic) in order to enhance their methane recovery. Results revealed that the methane recovery from digestate and solid separated digestate is feasible, considering their residual methane yields (70 NmL CH4/g VS and 90 NmL CH4/g VS, respectively). Thermal and alkaline post-treatments did not have a beneficial effect in enhancing methane potentials, while enzymatic post-treatment resulted in an increase of methane yield of 13% and 51% for SS-DIG and DIG samples, respectively. Finally, digestate recirculation permitted to obtain an extra electrical production (up to 4818 kWhel/day), which could represent an extra economical income to farmers.
Keywords: Anaerobic digestion; Digestate; Energy gain; Methane; Post-treatment;

Determination of kinetic and thermodynamic parameters of the B100 biodiesel oxidation process in mixtures with natural antioxidants by Kelly Roberta Spacino; Dionisio Borsato; Gabriela M. Buosi; Letícia Thaís Chendynski (366-370).
Biodiesel samples containing rosemary, oregano and basil extracts, free of alcohol, were submitted to oxidative stability tests at temperatures of 110, 115, 120 and 125 °C. The rate constants and enthalpy (ΔH), entropy (ΔS) and the Gibbs free energy (ΔG) in the activated state were determined from the experimentally obtained induction periods for evaluation of efficiency of natural antioxidants. A simplex-centroid mixture design was applied and the predictive equations were optimised simultaneously resulting in values of 85.89 kJ mol− 1 for ΔH, − 32.25 J K− 1  mol− 1 for ΔS and 98.48 kJ mol− 1  K− 1 for ΔG at ratios of 50% rosemary extract, 25% oregano and 25% basil. The results (ΔH  > 0; ΔS  < 0 and ΔG  > 0) showed that, in the presence of natural antioxidants, the oxidation reaction was endothermic and not spontaneous.
Keywords: Biofuel; Simplex-centroid; Enthalpy of activation; Entropy of activation; Gibbs free energy of activation;