Fuel Processing Technology (v.130, #C)
Editorial Board (IFC).
Continuous biodiesel production from acidic oil using a combination of cation- and anion-exchange resins by Benqiao He; Yixuan Shao; Yanbiao Ren; Jianxin Li; Yu Cheng (1-6).
A continuous process was developed to produce biodiesel from acidic oil containing soybean oil and oleic acid, which combined esterification by cation-exchange resin NKC-9, online separation and transesterification by anion-exchange resin D261. The esterification was carried out with soybean oil/oleic acid weight ratio of 5/5, methanol to oleic acid weight ratio of 1.5/1, reaction temperature of 338 K and residence time of 126.6 min. After the reaction, the mixture was settled to online separate into two layers, and the methanol–water–oleic acid mixture at the top layer was reclaimed. The bottom layer, mainly containing soybean oil and methyl oleate, was transesterified under methanol/soybean oil weight ratio of 1/3 and n-hexane/soybean oil weight ratio of 1/2 at 323 K for the residence time of 112.0 min. The high conversions of oleic acid (above 98%) and soybean oil (92.3%) were achieved. The yield of biodiesel in this process reached up to 95.1%. The main parameters of the product met the Chinese Standard of biodiesel.
Keywords: Esterification; Transesterification; Online separation; Continuous biodiesel production; Ion-exchange resins;
Acylation desulfurization of heavy cracking oil as a supplementary oil upgrading pathway by Xing-Yu Chen; Jia-Jun Gao; Ying-Zhou Lu; Hong Meng; Chun-Xi Li (7-11).
Acylation reaction is used to enhance the basicity and polarity of the thiophenes and thus promote their adsorptive removability by Lewis acid, forming an acylation desulfurization (ADS) process for the refractory sulfurs. The ADS performance of six acylating reagents (ARs) was assessed for heavy cracking oil and light oil at 303 K with AlCl3 as the catalyst, and the influence of ADS on the oil quality was also studied. The results show that ADS is efficient to remove the thiophenes, but less efficient for the removal of mercaptans and thioethers in light oil. S-removal rate of 90.9% was achieved for heavy cracking oil with acetyl bromide (AB)-AlCl3 (AB/S = 2/1; AlCl3/S = 5/1) in 0.5 h. The coexistent olefins and aromatics can slightly deteriorate the ADS performance and influence the oil properties. ADS might be used as a promising sulfur separating strategy for the cracking oil.
Keywords: Acylation; Heavy cracking oil;
Extraction of calcium from red gypsum for calcium carbonate production by Amin Azdarpour; Mohammad Asadullah; Radzuan Junin; Erfan Mohammadian; Hossein Hamidi; Ahmad Rafizan Mohamad Daud; Muhammad Manan (12-19).
Red gypsum can be considered as a long term storage of carbon dioxide through mineral carbonation. However, for the efficient carbonation, the calcium ions need to be extracted in the solution phase, followed by the carbonation reaction. Therefore, the extraction step is the key of successful mineral carbonation. In this study, solvent extraction of calcium and iron ions has been carried out using different types of acids and bases. In addition, the kinetic study of the extraction has also been performed. The study showed that the base solution was not capable of extracting significant amounts of calcium and iron, while acid solution was very efficient in extracting the ions. However, H2SO4 resulted in higher calcium extraction efficiency as compared to HCl and HNO3. Increasing reaction temperature from 30 to 70 °C and also increasing reaction time from 5 to 120 min were found to be effective in enhancing the degree of extraction for all the three acids used. Kinetic analyses found that the dissolution rate of red gypsum is controlled by the combination of product layer diffusion and chemical reaction control. The calculated activation energy of calcium extraction was 44.02, 37.68, and 42.73 kJ/mol for H2SO4, HCl and HNO3, respectively.
Keywords: Red gypsum; Mineral carbonation; Dissolution rate; Extraction efficiency; Kinetic analysis; Activation energy;
Effect of fatty acid composition in vegetable oils on combustion processes in an emulsion burner by J. San José; M.A. Sanz-Tejedor; Y. Arroyo (20-30).
The use of vegetable oils as a fuel in burners is an alternative which offers certain advantages over the use of vegetable oils in engines. The present work explores the use of four oils: rapeseed, sunflower, soya, and a commercial mixture-seed as heating fuel oil (HFO). The article relates the composition of the fatty acids in the various vegetable oils to the combustion products obtained in an emulsion burner. The work has been carried out in three stages. Firstly, describing the use of vegetable oils as a fuel and determining the fatty acid composition by proton NMR. Secondly, combustion of the vegetable oils studied is performed using an emulsion burner, varying the burner adjustments, and analysing combustion gases. Thirdly, exploring the link between the fatty acids contained in each oil and the combustion efficiency and combustion gas concentration for each oil type. Due to the fatty acids they contain, not all the oils behave equally, even though their description as fuels is very similar.
Keywords: Fatty acid composition; Vegetable oils; Combustion; Emulsion burner;
Catalytic decomposition of tar using iron supported biochar by James R. Kastner; Sudhagar Mani; Ankita Juneja (31-37).
Iron supported biochar catalysts were used to decompose toluene, a model tar compound, over a temperature range of 600–900 °C. Toluene conversion and decomposition rates increased linearly with increasing temperature and catalyst loading from 600 to 700 °C. Relative to biochar alone, the iron supported catalysts lowered the activation energy by 47% and decreased the formation of benzene, an intermediate in toluene decomposition. At 800 °C for the 13 and 18.7 wt.% iron loaded catalyst, toluene conversion approached 100% and benzene selectivity (SB) was zero, compared to an SB of 0.025% and 0.35% for 10% iron and the biochar, respectively. Time on stream studies with the 13 wt.% iron biochar catalyst, over the course of four days, resulted in a mean toluene conversion of 91% and benzene selectivity of 0.02%. These results indicate that inexpensive iron impregnated biochar catalysts could potentially be used to catalytically decompose tar molecules in syngas generated via biomass gasification.
Keywords: Biochar; Iron; Catalyst; Tar; Toluene; Reforming; Synthesis gas;
Synthesis of ionic liquids and their use for extracting nitrogen compounds from gas oil feeds towards diesel fuel production by Georgina C. Laredo; Natalya V. Likhanova; Irina V. Lijanova; Bernardo Rodriguez-Heredia; J. Jesús Castillo; Patricia Perez-Romo (38-45).
Seventeen ionic liquids (ILs), containing imidazole (7) and quaternary ammonium groups (10), were tested in the removal of nitrogen compounds present in the gas oil feed for diesel fuel production. A model mixture composed by quinoline, indole, and carbazole in hexadecane/toluene was used to run experiments with a Feed/IL ratio of 20/1 and 30 °C. In general, the synthesized ILs presented higher removals of indole and carbazole than of quinoline. Additionally, when the carbon number of the carboxylate counterpart of the quaternary ammonium ILs increased, the carbazole removal increased. Further experiments using model mixtures that contained also benzothiophene and benzothiophene and aniline, showed that none of these added compounds affected the ILs solubility for indole and carbazole under the same experimental conditions.Experiments carried out in a batch setup using straight run gas oil (SRGO) proved that only triethylmethylammonium butyrate and triethylmethylammonium acetate of all the ILs selected, presented good nitrogen removal capabilities and adequate chemical stabilities at the experimental conditions used. Therefore, they were chosen for a dynamic study that showed that a 30% organic nitrogen extraction could be attained when 200 and 170 mL per gram of material had passed before a regeneration process was required.Display Omitted
Keywords: Extraction; Nitrogen; Diesel; Denitrogenation; Ionic liquids;
Influence of metal addition to Ni-based catalysts for the co-production of carbon nanotubes and hydrogen from the thermal processing of waste polypropylene by Mohamad Anas Nahil; Chunfei Wu; Paul T. Williams (46-53).
This paper investigates the co-production of hydrogen and carbon nanotubes from the pyrolysis–catalytic gasification of waste plastics (polypropylene). We report on the influence of a range of metal additions to a nickel based catalyst based on ternary mixed oxide types Ni–Metal–Al, where the metal was Zn, Mg, Ca, Ce or Mn. The results showed that of the different metal–nickel catalysts investigated, the Ni–Mn–Al catalyst was the most promising catalyst in relation to the co-production of hydrogen and CNT. For example, the Ni–Mn–Al catalyst produced 71.4 mmol hydrogen g− 1 plastic, while the hydrogen production using Ni–Ca–Al, Ni–Ce–Al and Ni–Zn–Al catalysts were 68.5 mmol g− 1, 63.1 mmol g− 1 and 45.9 mmol hydrogen g− 1 plastic respectively. In addition, carbon deposition on the catalyst was highest in the order of: Ni–Mn–Al > Ni–Ca–Al > Ni–Zn–Al > Ni–Ce–Al > Ni–Mg–Al. The carbon deposition for the Ni–Mn–Al catalyst was found to consist of mostly carbon nanotubes. Further investigation of the Ni–Mn–Al catalyst demonstrated that the interaction between Ni and catalyst support plays a significant role in the gasification process; weak metal support interaction (for the Ni–Mn–Al catalyst calcined at 300 °C) resulted in a lower hydrogen production and much higher yield of carbon products. In addition, the influence of steam injection rate on hydrogen and carbon nanotube production was investigated for the Ni–Mn–Al catalyst. Increasing the steam injection rate significantly increased hydrogen production and decreased carbon deposition. However, at lower steam injection rates, the quality of the product carbon nanotubes was improved.Display Omitted
Keywords: Waste; Reforming; Gasification; Plastic; Hydrogen; Carbon nanotubes;
Reactive distillation in conventional Fischer–Tropsch reactors by Cornelius Mduduzi Masuku; Xiaojun Lu; Diane Hildebrandt; David Glasser (54-61).
The Flory distribution that is often observed in Fischer–Tropsch (FT) reactors could be described by reaction equilibrium between species. Furthermore, it has been suggested that vapour–liquid equilibrium (VLE) exists in the reactor and this could cause the two-alpha product distribution that is often observed experimentally. Simultaneous reaction and VLE lead us to ask the question: can we not describe the FT reaction as a reactive distillation system? In this paper we develop a mathematical model to describe the behaviour and performance of an FT reactor by considering the dynamic interaction between reaction and VLE. The model results show that the rate of formation of component hydrocarbons is dependent on either the reaction rate or stripping rate, depending on which one is rate-limiting. Furthermore we show that at steady state, the rate of formation of hydrocarbons is proportional to the stripping rate. We conducted an experiment which showed a reaction rate increment when the reactor was switched from CSTR to batch mode. The CO rate increases because reactant stripping was limiting the reaction rate. Modelling an FT reactor as a reactive distillation column is also consistent with the two-alpha positive deviation product distribution observed experimentally and industrially.Display Omitted
Keywords: Reactive distillation; Vapour–liquid equilibrium; Product distribution; Fischer–Tropsch batch reactor;
Thin-layer drying characteristics and modeling of Ximeng lignite under microwave irradiation by Jie-Feng Zhu; Jian-Zhong Liu; Jun-Hong Wu; Jun Cheng; Jun-Hu Zhou; Ke-Fa Cen (62-70).
The thin-layer drying characteristics of Ximeng lignite (XL) were investigated under microwave irradiation, and mathematical modeling using thin-layer drying models from literature was performed. The effects of coal particle size and microwave power level on drying characteristics were studied. The drying rate increased and drying time decreased with increasing particle size or microwave power level. The drying rate and drying rate to moisture ratio curves, which contained a constant rate period at lower microwave output powers, exhibited fast heating and falling rate periods at different coal-particle sizes and microwave output power levels. Among the 14 thin-layer drying models proposed, the Midilli–Kucuk model provided a better fit for all applied drying conditions and could be used to estimate moisture in XL at any time during the microwave-drying process after running a multiple regression analysis. The drying rate constants and apparent diffusion coefficients (determined from the Midilli–Kucuk model and Fick's second law, respectively) increased with increasing particle size or microwave power level. The activation energy estimated from a modified Arrhenius equation was Ea = 77.0485 W/g. The equilibrium moisture of XL decreased with increasing microwave output power or decreasing particle size.
Keywords: Lignite; Microwave drying; Drying kinetic; Thin-layer drying; Moisture reabsorption;
Promotional effect of cerium on Mo–V–Te–Nb mixed oxide catalyst for ammoxidation of propane to acrylonitrile by Guojun Wang; Yun Guo; Guanzhong Lu (71-77).
The MoV0.31Te0.23Nb0.24 mixed oxide (M) catalysts with different cerium amounts for propane ammoxidation to acrylonitrile were synthesized by the co-precipitation method. The effect of cerium content on the physicochemical property of the M catalyst was investigated by low-temperature N2 adsorption, XRD, XPS and H2-TPR. The results show that the presence of cerium in the M catalyst can significantly enhance its catalytic performance for propane ammoxidation. 46% acrylonitrile yield can be obtained over the MCe0.05 catalyst with Ce/Mo = 0.05 (mol) at SV of 1200 mL/(h.g), in which there are most optimal surface compositions, such as more M1 and M2 active phases, and higher Te4 + concentration and appropriate V content. The presence of Ce3 +/Ce4 + pairs promotes the redox capability of the M catalyst and more reasonable atom distribution on the catalyst surface.
Keywords: Propane ammoxidation; Mo–V–Te–Nb mixed oxide catalyst; Cerium promoter; Manufacture of acrylonitrile;
Proton transfer reaction-mass spectrometry as a rapid inline tool for filter efficiency of activated charcoal in support of the development of Solid Oxide Fuel Cells fueled with biogas by Davide Papurello; Erna Schuhfried; Andrea Lanzini; Andrea Romano; Luca Cappellin; Tilmann D. Märk; Silvia Silvestri; Massimo Santarelli; Franco Biasioli (78-86).
Efficient power technologies such as high temperature fuel cells demand ultra-low concentrations of contaminants in the fuel feed e.g. < 1 ppm(v), imposing stringent requirements on fuel clean-up technology. Proton transfer reaction-mass spectrometry (PTR-MS), being fast and suitable to measure ultra-low concentrations can be an optimal tool for the characterization of clean-up methods. It is exploited here for the simultaneous measurement of breakthrough curves of biogas filters loaded with a mix of compounds that simulate biogas pollutants. The sorbent materials are able to efficiently remove propanethiol and butanethiol and to a lesser degree methanethiol and hydrogen sulfide. Carbon disulfide and dimethylsulfide were the compounds that elute from the filters. These results support the development of set-ups for the cleaning of real biogas from the Organic Fraction of Municipal Solid Waste (OFMSW) and its use for Solid Oxide Fuel Cell (SOFC) feeding.Display Omitted
Keywords: Proton transfer reaction-mass spectrometry (PTR-MS); Biogas; Solid Oxide Fuel Cell (SOFC); Volatile organic sulfur compounds (VOSCs); Desulfurization; Filter breakthrough curves;
Residence time distributions of coarse biomass particles in a screw conveyor reactor by R.W. Nachenius; T.A. van de Wardt; F. Ronsse; W. Prins (87-95).
Rotating screw conveyors can be utilized in the application of heat to granular materials: the mechanical motion of the rotating screw provides a controlled means of transferring the product through different thermal sections. This is particularly interesting for thermochemical biomass reactor applications such as slow pyrolysis and torrefaction. To understand the transfer of heat to the biomass, it is necessary to predict the residence time distribution of the material within the rotating screw reactor. Experiments were performed using a bench-scale (2.5 kg/h) rotating screw conveyor. In this work, it has been shown that an empirical mathematical model is sufficient for predicting the mean residence time of various materials (pine chips of different sizes, rice and sand) if the rotational frequency of the screw conveyor and the volumetric throughput rate are both known. The model parameters obtained in this work were found to be independent of material selection but are specific to the geometry of the screw reactor. The form of the mathematical model proposed in this work may be applied to similar applications. Unlike the mean residence times, the axial dispersion calculated from the experimental data showed greater variability and this precluded any predictive modeling.
Keywords: Screw conveyor; Residence time distribution; Axial dispersion; Biomass;
Products analysis of Shendong long-flame coal hydropyrolysis with iron-based catalysts by Jie Feng; Xiaoyong Xue; Xiaohong Li; Wenying Li; Xiaofen Guo; Ke Liu (96-100).
This paper focuses on the effect of Fe2O3, Fe2S3, Fe2O3-oleic acid, FeS, and FeSO4 on hydropyrolysis of Shendong long-flame coal. The experiments were conducted at 650 °C and 0.1 MPa in a novel lab-scale-fixed-bed reactor. For non-catalytic hydropyrolysis process, the char, tar and gas yields were 73.5 wt.%, 7.9 wt.%, and 12.1 wt.%, respectively. In terms of catalytic hydropyrolysis, the highest conversion of coal and tar yields (8.4 wt.%) was observed when Fe2O3-oleic acid was used. The strong decomposition capability of the iron-based catalysts had negative effects on the tar yield, but favored the formation of the n-hexane soluble compounds. Particularly with Fe2S3 as a catalyst, the tar yield decreased from 7.9 wt.% to 7.0 wt.%, while the n-hexane soluble contents of the tar increased from 70.6 wt.% to 81.0 wt.%. The yield of lightweight components increased about 0.1 wt.%. A molecular weight reduction in the tar and the heavy compounds, which confirmed the ability of iron-based catalysts to make the heavy oil be light. The characteristic temperatures of char gasification with CO2 had little change.Display Omitted
Keywords: Shendong long-flame coal; Hydropyrolysis; Iron-based catalyst; Products distribution;
Study on lignite dewatering by vibration mechanical thermal expression process by Yixin Zhang; Jianjun Wu; Jiang Ma; Binbin Wang; Xiaoling Shang; Chongdian Si (101-106).
A new dewatering process — vibration mechanical thermal expression (VMTE) process developed from mechanical thermal expression (MTE) process was studied in this paper. The enhancement of moisture content reduction of Zhaotong lignite by vibration in VMTE process under different temperatures and pressure was determined. Compared to MTE process, the dewatering efficiency was enhanced by 10% by VMTE process with a vibration force of 5 kN in tested range. The moisture content decreased from 1 to 0.19 (g/g) (db) under the most severe processing conditions. The investigation was carried out to identify how variations in vibration force affect the dewatering during the VMTE process. The vibration was proved to enhance the volume reduction of lignite samples which is closely related to the decrease of moisture content by accelerating particle compaction and the change of coal structure. The increase of vibration force in a special range resulted in more severe reduction of moisture content than that out of the range. The reduction of moisture content caused by the vibration force increase in the range from 1 kN to 4 kN was 3.6 times that in the range from 0 to 1 kN. A limitation of dewatering caused by the increase of vibration force was expected to exist.
Keywords: Vibration; Mechanical thermal expression; Lignite; Dewatering;
Catalytic CO2 gasification of a Powder River Basin coal by Fan Zhang; Deping Xu; Yonggang Wang; Yan Wang; Ying Gao; Tiberiu Popa; Maohong Fan (107-116).
CO2 gasification of Wyodak low-sulfur sub-bituminous coal from the Powder River Basin (PRB) of Wyoming was conducted in a fixed-bed laboratory gasifier at atmospheric pressure with Na2CO3, an inexpensive catalyst widely available in Wyoming. The sodium effect on the coal pyrolysis and the sodium forms existing during the char gasification were investigated using thermo-gravimetric analyses (TGA) and X-ray diffraction (XRD) analyses, respectively. Sodium was found to decrease the tar production and promote the char condensation during the pyrolysis. The interaction between added sodium and the minerals in Wyodak coal were observed during the char gasification. Grain, integrated, and random pore models were employed to fit the kinetic data obtained under both non-catalytic and catalytic conditions. The apparent activation energies of the coal-CO2 gasification without and with use of the catalyst (3 wt.% Na) are ~ 91 kJ/mol and ~ 64 kJ/mol, respectively, a 30% decrease. Thus, Na2CO3 is a promising catalyst for the PRB coal-CO2 gasification.Display Omitted
Keywords: CO2; Coal gasification; Na2CO3; XRD; Kinetic model;
Reaction mechanism and kinetic modeling of hydroisomerization and hydroaromatization of fluid catalytic cracking naphtha by Zhiping Chen; Jian Xu; Yu Fan; Gang Shi; Xiaojun Bao (117-126).
Hydroisomerization and hydroaromatization of fluid catalytic cracking (FCC) naphtha and model hydrocarbons were investigated over a Ni–Mo/Al2O3–HZSM-5 octane recovery catalyst, and a general mechanistic pathway was proposed. A twenty-two lump kinetic model was presented based on n-paraffin, i-paraffin, olefin, naphthalene, and aromatics (PIONA) analyses. Furthermore, an octane number prediction model based on the composition of the kinetic lumps was developed. The experimental results showed that the main reactions occurring are dimerization, cracking, isomerization and aromatization of olefins. Isomerization and aromatization are very advantageous for the olefin reduction and octane number preservation of FCC naphtha in hydro-upgrading. The reaction mechanism pathway under industrial conditions mainly includes two stages: olefin interconversion and olefin aromatization, accompanied with olefin saturation. The parameters in the kinetic model and octane prediction model were estimated from experimental data and the results showed that the model predictions were in good agreement with experimental results.Hydroisomerization and hydroaromatization of fluid catalytic cracking naphtha and model hydrocarbons were investigated over a Ni–Mo/Al2O3–HZSM-5 octane recovery catalyst, and a general mechanistic pathway was proposed. A twenty-two lump kinetic model was presented based on n-paraffins, i-paraffins, olefins, naphthalenes, and aromatics analyses.Display Omitted
Keywords: Kinetic model; FCC naphtha; Hydroisomerization; Hydroaromatization; Reaction mechanism; Octane recovery;
Investigation of the factors affecting the progress of base-catalyzed transesterification of rapeseed oil to biodiesel FAME by James Pullen; Khizer Saeed (127-135).
Conventional base-catalyzed transesterification method for large scale biodiesel FAME production is affected by a number experimental factors. This work investigates, quantifies and establishes the effects of catalyst type, number of reaction stages, the free fatty acid (FFA) and water content of the reactants on the progress of rapeseed base-catalyzed transesterification under the optimized reaction conditions used in scale-up production. Firstly, the efficacy of different alkaline-base catalysts: sodium hydroxide (NaOH), potassium hydroxide (KOH), and sodium methoxide (CH3ONa) were investigated and compared. The order of catalyst efficacy was found to be NaOH > CH3ONa > KOH at 1% m/m concentration: NaOH was most potent achieving the highest conversion to FAME in the shortest time. The effect of performing a 2 stage base-catalyzed reaction, where glycerol was removed prior to a second reaction stage, was investigated to determine any increase in the overall conversion to FAME relative to the single stage process. The effects of increasing the reactant FFA and water content on completeness of transesterification using 1% m/m NaOH were also studied. End-product FAME content was significantly reduced at > 5% m/m acid content (acid value > 10 mg KOH/g). Above ~ 7% m/m acid (~ 14 mg KOH/g), the reaction was stopped due to excessive soap/gel formation. The FAME content was not especially sensitive to reactant water contamination. Only at a water level of > 6000 ppm was the FAME content.
Keywords: Biodiesel; Fatty acid methyl esters (FAME); Transesterification; Catalyst;
Proton transfer reaction mass spectrometry technique for the monitoring of volatile sulfur compounds in a fuel cell quality clean-up system by Davide Papurello; Lorenzo Tognana; Andrea Lanzini; Federico Smeacetto; Massimo Santarelli; Ilaria Belcari; Silvia Silvestri; Franco Biasioli (136-146).
Biogas from the dry anaerobic digestion of OFMSW from a pilot plant was analyzed in terms of sulfur compound removal through a gas cleaning section based on activated carbons, from lab. scale to real plant. In general, even the presence of sub-ppm(v) of selected biogas contaminants can hamper the life-time of SOFC systems. For this reason, stringent fuel cell quality requirements apply. The challenge of real-time monitoring of the performance and quality of the fuel feeding the SOFC can be solved through the use of PTR-MS. This technique – once properly and preliminary calibrated as shown in this study – has the capability of rapidly resolving the wide spectrum of contaminants slipping from the clean-up section. A commercial sorbent material was adopted to remove sulfur compounds and was tested for 80 h in a pilot gas cleaning system. H2S, the main sulfur compound detected (99.36% of total sulfurs) was removed to a satisfactory level. The sulfur compounds elute from the cleaning section in the following order: CH3SH, CH3SCH3, CH3CH2CH2SH, CH3(CH2)3SH, CS2 and H2S. The filter section was able to provide a clean biogas (1 ppm(v)) throughout the whole experimental trial (almost 450 h) with an average H2S inlet concentration of 52 ppm(v).
Keywords: Volatile sulfur compounds (VSCs); Biogas; Solid oxide fuel cell (SOFC); Organic fraction of municipal solid waste (OFMSW); Proton transfer reaction-mass spectrometry (PTR-MS);
Isoconversional kinetic analysis of olive pomace decomposition under torrefaction operating conditions by Paola Brachi; Francesco Miccio; Michele Miccio; Giovanna Ruoppolo (147-154).
Kinetic analysis of the olive pomace thermal degradation in the temperature range of interest for torrefaction was performed by using non-isothermal thermogravimetric measurements at different heating rates, ranging from 2 to 40 °C/min. A comparison is presented between two selected integral isoconversional methods, i.e., the nonlinear Vyazovkin incremental approach, which is more accurate but time-consuming, and the linear Ozawa–Flynn–Wall (OFW) method, which is less accurate but computationally simpler. Results show that the values of the activation energy by the OFW method are consistent with the ones provided by the Vyazovkin approach. This implies that the OFW method, more user-friendly compared to the Vyazovkin procedure, is suitable for studying the torrefaction kinetics of residual biomass, such as olive pomace. The reliability of the OFW method was further confirmed by the successful application of the derived kinetic data to reproduce (i.e., predict) experimental TG curves not included in the kinetic computations.Configurational and granular temperatures increase with the increase of amplitude and frequency of moveable grates.Display Omitted
Keywords: Kinetic analysis; Bio-waste; Torrefaction; Thermogravimetric analysis; Isoconversional method;
Pore size effects on Ru/SiO2 catalysts with Mn and Zr promoters for Fischer–Tropsch synthesis by Mohammad Nurunnabi; Scott Q. Turn (155-164).
The effects of pore size on Ru/SiO2 catalyst performance were investigated for Fischer–Tropsch synthesis under the conditions of 503 K, 20 bar and 1800 h− 1. Ru/SiO2 with 10 nm pore size catalyst showed higher catalytic activity than Ru/SiO2 catalysts with 3, 6 and 30 nm pore sizes. The 10 nm pore size, Ru/SiO2 catalyst exhibited uniform pore diameter, an increased surface concentration of active Ru metals, and the increased dispersion of Ru on the surface compared to the other pore diameters. Deactivation was clearly observed for all Ru/SiO2 catalysts during the reaction. The addition of small amounts of Zr and Mn (1:30, Zr or Mn:Si) improved catalytic activity and stability for Fischer–Tropsch synthesis. The deactivation rate of Ru/Zr/Q10 was about 21% at 51 h time on stream and this rate was much lower than Ru/Q10 (57%). Ru/Mn/Q10 showed higher catalytic activity than Ru/Q10 and Ru/Zr/Q10, and its deactivation rate was much lower ~ 9% after 51 h time on stream. The small amount of Mn added to the Ru/SiO2 increased the concentration of active Ru metals and enhanced their dispersion on the support surface.Display Omitted
Keywords: Pore size; Ru/SiO2 catalyst; Mn and Zr addition; Fischer–Tropsch synthesis; Catalyst activity; Deactivation rate;
Dependence of onset time for mesophase formation on operating parameters during catalytic hydroconversion of Athabasca vacuum residue by Mohamed Sharshar; S. Reza Bagheri; William C. McCaffrey; Murray R. Gray (165-171).
During the catalytic hydroconversion of vacuum residue fractions of bitumen or petroleum, the formation of mesophase can lead to fouling of reactor internals. In this study we examine the dependence of the onset of mesophase in a batch microreactor designed to enable in situ microscopic observation of the reacting liquid. The following process variables were investigated: temperature, partial pressure of hydrogen, catalyst concentration, agitation speed, and their interactions. Athabasca vacuum residue was converted in the presence of an iron sulfide particulate catalyst, and a statistical model was developed to describe the effects of the process variables on the onset time for mesophase formation. The temperature and catalyst concentration, respectively, had the most effect on mesophase onset time. The time for mesophase formation dropped by 12.1 min when the operating temperature increased from 440 °C to 450 °C. The mesophase onset time increased by 7.4 min when 3 wt.% of catalyst was added at 440 °C, compared to no catalyst addition. Partial pressure of hydrogen was not significant as an independent process variable for the range studied, from 2.4 to 5.2 MPa. The combined effects of hydrogen partial pressure and catalyst concentration were significant, as were the combined effects of temperature and catalyst concentration.
Keywords: Mesophase; Coking; Fouling; Bitumen; Heavy oil; Hydroconversion;
Digestate as bio-fuel in domestic furnaces by Simone Pedrazzi; Giulio Allesina; Tobia Belló; Carlo Alberto Rinaldini; Paolo Tartarini (172-178).
This study investigates the use of the biogas power plants byproduct (digestate) as biofuel in an ordinary domestic air furnace. The digestate, disposed by a 1 MW biogas plant located in Italy, was dried out and pelletized in order to be used as fuel in a wood pellet furnace with 29 kW th of nominal power, commonly installed in industrial HVAC systems. The first test was carried out starting from a heavily dried pellet called “digestate 0” characterized chemically and physically in order to obtain its composition, while its ashes were tested using an optical thermal dilatometer for the softening point evaluation. This first test outlined that the “digestate 0” pellets were not suitable for combustion applications even when mixed with an equal part of pure wood pellets. The research then focused on the raw digestate drying process through a set of physical and chemical tests. It was found that a temperature of 150 °C maximizes the higher heating value of the new “digestate 1” at 16.6 MJ/kg. However, to further avoid the ash sintering, “ultimate digestate” pellets were prepared mixing 50% of “digestate 1” and 50% of wood. The digestate obtained in such a way was experimentally tested through several runs of the air furnace. In these tests, the overall efficiency as well as the furnace emissions was measured.
Keywords: Digestate; Solid biofuel; Pellet; Domestic furnace; Sintering;
Catalytic destruction of chlorobenzene over mesoporous ACeO x (A = Co, Cu, Fe, Mn, or Zr) composites prepared by inorganic metal precursor spontaneous precipitation by Chi He; Bi-Tao Xu; Jian-Wen Shi; Nan-Li Qiao; Zheng-Ping Hao; Jing-Lian Zhao (179-187).
Mesostructured ACeO x (A = Co, Cu, Fe, Mn, or Zr) composites with large specific surface area and developed mesoporosity were prepared by inorganic metal precursor spontaneous precipitation (IMSP) method. Influences of catalyst surface area, pore structure, reducibility, and active oxygen concentration on catalytic performance were studied. Both preparation route and metal precursor type affect metal active site dispersion, and the IMSP is a desirable approach for synthesis of metal composites with homogeneous active phase distribution. The original crystalline structure of CeO2 is well maintained although parts of transition metal cations are incorporated into its framework. The forming of A n+–O2 −–Ce4 + connections in ACeO x catalysts could reduce the redox potential of metal species, allowing effective redox cycles during oxidation reactions. CuCeO x demonstrates powerful catalytic efficiency with 99% of chlorobenzene (CB) destructed at 328 °C, which is much lower than the other ACeO x oxides and Cu-doped catalysts synthesized via the incipient impregnation and coprecipitation methods (T99 > 405 °C). The active site reducibility is the foremost activity determining factor for CB destruction.
Keywords: Mesostructured oxides; Homogeneous precipitation; Transition metal; Catalytic oxidation; Chlorobenzene; CVOCs;
A vital stage in the large-scale production of biofuels from spent coffee grounds: The drying kinetics by Francisco J. Gómez-de la Cruz; Fernando Cruz-Peragón; Pedro J. Casanova-Peláez; José M. Palomar-Carnicero (188-196).
Spent coffee grounds are being consolidated as one of the most abundant bioresources in the world for use as green energy. Biodiesel, bioethanol, bio-oil and fuel pellet are biofuels derived of this waste. To get them, spent coffee grounds need to be dried due to their high moisture content. This work analyzes their drying kinetics from isothermal drying experiments in a convective dryer at different temperatures: 100, 150, 200 and 250 °C, and sample thicknesses: 5, 10, 15 and 20 mm. Drying curves were fitted with the main mathematical models in the drying of agricultural products where the Two Term Gaussian model got the best results of fit. Drying rate was calculated and analyzed. Effective moisture diffusivities were calculated in a range between 1.29 · 10− 9 to 28.8 · 10− 9 m2/s. Activation energies were 12.29, 12.78, 15.18 and 16.87 kJ/mol for each sample thickness: 5, 10, 15, and 20 mm, respectively.
Keywords: Spent coffee grounds; Drying rate; Biofuels; Drying kinetics; Effective moisture diffusivity;
Air–steam gasification of biomass in fluidized bed with CO2 absorption: A kinetic model for performance prediction by C.C. Sreejith; C. Muraleedharan; P. Arun (197-207).
Significance of decarbonized energy production in the context of a foreseeable hydrogen economy has called for the need of extensive research in biomass gasification-carbon dioxide capture technique. The feasibility of calcium oxide as a sorbent for CO2 in syngas is studied for air–steam fluidized bed (FB) gasification through a reaction kinetic modeling approach. Arrhenius rate equations are employed for primary and secondary pyrolysis, gasification and carbonation reactions. Devolatilization product yields are predicted using available correlations for FB gasification and cracking of tar is incorporated. Parametric performance analysis is carried out highlighting the significance of equivalence ratio (ER), gasification temperature, steam to biomass ratio (SBR) and sorbent to biomass ratio (SOBR). The effects of various gasifying media on H2 concentration and performance indicators such as heating value and efficiencies are analyzed. The simulation results are validated with the reported experimental results. The kinetic study reveals that air–steam gasification significantly reduces the unreacted steam but at a lower H2 concentration than steam gasification. A maximum of 53% hydrogen rich gas mixture is predicted at ER = 0.25, SBR = 1.5, SOBR = 2.7 and 1000 K. Against fossil fuel expended steam gasification, pure oxygen gasification is suggested by the study.
Keywords: Air–steam gasification; Kinetic model; CO2 absorption; Hydrogen concentration;
Drying kinetics of coarse lignite particles in a fixed bed by Saban Pusat; Mustafa Tahir Akkoyunlu; Hasan Hüseyin Erdem; Ahmet Dağdaş (208-213).
In this study, experimental works for a Turkish lignite in a fixed bed dryer were carried out. Drying experiments were carried out at 70, 100 and 130 °C drying air temperatures, 0.4, 1.7 and 1.1 m/s drying air velocities, 80, 130 and 150 mm sample heights and 20, 35 and 50 mm sample sizes. Suitability of twelve thin-layer drying models in describing the drying kinetics of lignite was evaluated by using statistical analyses. The results show that Wang&Singh model is the best model describing the drying behavior of coarse lignite particles in a fixed bed dryer, which is different from the literature. Additionally, the effects of drying parameters on model coefficients were studied by multiple regression analysis. Finally, apparent diffusion coefficient range was presented.
Keywords: Lignite; Drying kinetics; Fixed bed; Modeling; Turkey;
Adsorptive desulfurization using different passivated carbon nanoparticles by PEG-200 by Rahimeh Naviri Fallah; Saeid Azizian; Amarendra Dhar Dwivedi; Mika Sillanpää (214-223).
Carbon nanoparticles dispersed in aqueous phase (CNPs) were synthesized using different poly(ethylene glycol) (PEG 200) assistant solution methods including microwave pyrolysis and alkali-assisted heating, ultrasonication, and refluxing. The CNPs (< 5 nm) were used for the selective removal of sulfur thiophenic compounds (benzothiophene (BT), dibenzothiophene (DBT) and dimethyldibenzothiophene (DMDBT)) from liquid model fuels including aromatic compounds (naphthalene (NP) and 1-methylnaphthalene (MNP)). The presence of PEG in the preparation procedure of CNP was crucial and adsorption capability was related to the passivation by PEG. The decomposition of PEG at high temperature introduced more acidic functional groups on the carbon framework and also promoted the formation of porous CNP nanostructures because of hydrophobic PEG aggregations. Adsorption experiments showed the order for CNPs with different method as: microwave irradiation > heating > refluxing > ultrasonication. The highest efficiency of CNPs by microwave-assisted technique for sulfur removal was examined due to the higher decomposition of PEG and more porosity of CNP nanostructures which were produced at higher temperature. Moreover the CNPs were regenerable by a solvent-washing process. This study showed that passivated CNPs are very effective for rapid desulfurization of liquid fuels, operating at ambient conditions with the ease of separation and regeneration.
Keywords: Carbon nanoparticles; Desulfurization; Liquid fuel; Adsorption;
Laboratory screening tests on the effect of initial oil saturation for the dynamic control of in-situ combustion by Denis Aleksandrov; Berna Hascakir (224-234).
There are two main goals of this study: to investigate the performance variations of in-situ combustion (ISC) with the change in initial oil saturation (IOS) through laboratory screening tests and to determine mechanisms for maintaining the dynamic control of ISC by varying the injected air rate in an oil field which has heterogeneously distributed IOS. Thus, we start with the determination of the optimum IOS value for ISC with five combustion tube tests at identical experimental conditions but at different IOS values and the IOS value used in the best performing experiment is decided to be the optimum IOS value for the given experimental conditions. Then, the air-requirement for the field-scale application is calculated analytically. The air-requirements for the experiments which exhibit poorer performance are normalized according to the value obtained for the optimum IOS case. We observed that the fuel-deposition amount is highly affected by the IOS and decreases with IOS. Our findings show that the constant air rate used in the experiments is responsible for the performance change in ISC for varying IOS. Therefore, the air rate should be adjusted according to the estimated fuel deposition amount for the dynamic control of ISC for the field application.
Keywords: In-situ combustion; Initial oil saturation; Fuel–air ratio; Canadian oil sand; CT scanner;
Prediction of formation of gas-phase bubbles correlated by vortices in the fuel reactor of chemical looping combustion by Luming Chen; Xiaogang Yang; Xia Li; Guang Li; Colin Snape (235-244).
Chemical looping combustion (CLC) as a potential CO2 capture technology has been considered as a promising and likely alternative to traditional combustion technology to mitigate the CO2 emission due to its prosecution of CO2 sequestration at a low cost. Although a number of studies on the hydrodynamic behaviours of the CLC process in fuel reactor have been documented in the open literature, there have been rare studies on the correlation between the bubble formation and the local particulate volume fraction. This paper aims to investigate the CLC process in a fuel reactor using the CFD modelling, coupled with the heterogeneous reactions, the hydrodynamics and reaction kinetics occurring in the fuel reactor. A parameter correlating the occurrence of bubble and dynamic properties is proposed. The parameter may be acted as an indicator of time-dependent bubble evolution with a potential to be adopted in the CLC for controlling the bubbling phenomena since the occurrence of the bubbles at specific positions is highly correlated with the local large eddies embedded in the flow. The results obtained clearly indicate that the CFD model developed in the current study reasonably forecasts the hydrodynamic behaviours and important phenomena observed in the fuel reactor.
Keywords: Chemical looping combustion; Fuel reactor; CFD; Fluidised bed;
Assessment of shelf life of Bulgarian industrial FAME by the use of modified ASTM D2274 as accelerated oxidation method by Rosen K. Dinkov; Dicho S. Stratiev; Ivelina K. Shishkova; Slavi K. Ivanov; Tanya T. Tsaneva; M. Mitkova; M. Skumov (245-251).
Kinetic data for hydroperoxide formation in a commercial biodiesel, produced from 50% sunflower oil and 50% rapeseed oil were obtained by using rapid, higher than standard temperature procedure with sufficient oxygen solubility in the samples. Three different mathematical methods for processing the data and shelf life determination of the studied biodiesel are compared. The applicable methodologies are hydroperoxide concentration abrupt increase graphical determination and Q rule. The calculation shows that shelf life of the studied stabilized Bulgarian biodiesel amounts between 1.17 and 1.27 years. It was also found that peroxide value for induction period at 15 °C is 71.8 meq O2/kg biodiesel.
Keywords: Biodiesel; Shelf life; Peroxide value; Induction period; Q rule;
Catalytic post-treatment of the vapors from sewage sludge pyrolysis by means of γ-Al2O3: Effect on the liquid product properties by M. Azuara; I. Fonts; F. Bimbela; M.B. Murillo; G. Gea (252-262).
The present work describes an experimental study on sewage sludge pyrolysis in a bubbling Fluidized Bed Reactor (FluBR) and the effect of a catalytic post-treatment of the hot pyrolysis vapors on the pyrolysis liquid product properties, using gamma-alumina (γ-Al2O3) as a catalyst in a secondary Fixed Bed Reactor (FixBR) placed downstream from the FluBR reactor. The catalytic treatment improved the pyrolysis liquid phase separation, obtaining a liquid with a single organic phase instead of the two usually obtained in sewage sludge pyrolysis without applying γ-Al2O3. The catalytic post-treatment yielded enhanced organic phases with improved properties (higher heating value, stability, viscosity and chemical composition) and only a minor decrease in the liquid yield. The improvement in the liquid properties was caused by a reduction in the proportion of oxygen-containing compounds. In addition, its composition and physicochemical properties could make it a potential raw material for its co-processing in conventional refineries along with crude oil or oil-derived fractions, if the problem of the high nitrogen content in the liquid is alleviated.
Keywords: Pyrolysis; Sewage sludge; Gamma-alumina; Catalytic treatment; Bio-oil;
Microwave synthesis of thermal insulating foams from coal derived bottom ash by Ehsan Ul Haq; Sanosh Kunjalukkal Padmanabhan; Antonio Licciulli (263-267).
Bottom ash from coal-fired power plants is a potential raw material for the production of ceramic tiles, bricks and blocks for various applications. In this work we are presenting a novel microwave method to utilize the bottom ash to produce thermal insulating bricks. Foam samples were prepared by microwave foaming of the mortar prepared by milling the bottom ash, sodium silicate and NaOH. The microwave foaming ability of different slurry compositions and the physical and mechanical properties of the foamed samples were evaluated. FTIR analysis reveals that the degree of geopolymerization increases with increasing fraction of sodium silicate. Foams with low bulk density, high porosity, low thermal conductivity and compressive strengths were obtained by this method. With varying the bottom ash to sodium silicate ratio, it is possible to modulate the physical and mechanical properties of the insulating bricks.
Keywords: Bottom ash; Microwave foaming; Geopolymer; Thermal insulation; Mechanical strength;
Hydrothermal processing of macroalgae for producing crude bio-oil by Yu-Ping Xu; Pei-Gao Duan; Feng Wang (268-274).
In this study, a green marine macroalga—Enteromorpha prolifera was hydrothermally treated by using a fast-heating rate batch reactor over different temperatures (250–390 °C), retention times (10–120 min), algae/water mass ratios (0.5/8.4–5.5/8.4), and K2CO3 loadings (0–30 wt.%). The yields of products (crude bio-oil (CBO), solid residue, gas, and water-soluble products) were affected by all the operating variables. Under conditions of an algae/water mass ratio of 3.5/8.4 and K2CO3 loading of 20 wt.%, the highest CBO yield of 34.7 wt.% on dry ash-free basis was achieved at 370 °C for 60 min. The C and H contents of the CBO are much higher than those of the algal biomass feedstock, whereas the O content in the CBO was significantly reduced to 6.9 wt.% (vs. 19.3 wt.% in the feedstock). The typical calorific value of the CBO was estimated at around ca. 39.4 kJ/g. About 48% of the chemical energy in the macroalga biomass could be recovered in the CBO fraction. This study demonstrates the feasibility of applying hydrothermal liquefaction to produce CBO from macroalgae with high ash content.Display Omitted
Keywords: Hydrothermal liquefaction; Macroalgae; Enteromorpha prolifera; Crude bio-oil;
Effects of intake air temperature on combustion, performance and emission characteristics of a HCCI engine fueled with the blends of 20% n-heptane and 80% isooctane fuels by Can Cinar; Ahmet Uyumaz; Hamit Solmaz; Fatih Sahin; Seyfi Polat; Emre Yilmaz (275-281).
In this study, the effects of intake air temperature on the cylinder pressure, heat release rate, start of combustion, combustion duration, engine performance and exhaust emissions were investigated in a HCCI gasoline engine fueled with the blends of 20% n-heptane and 80% isooctane fuels. Intake air temperature was changed from 40 °C to 120 °C. The experiments were performed with a single-cylinder, four-stroke HCCI gasoline engine at two different excessive air coefficients at 1200 rpm. The results showed that in-cylinder pressure and heat release rate increased with the increase of intake air temperature. The increase of intake air temperature caused combustion to advance and the combustion duration to decrease. At 70 °C intake air temperature, brake torque decreased by 3.1% when the engine operated with λ = 0.6 compared to λ = 0.7. The specific fuel consumption and NO emissions tend to increase at higher intake air temperatures of 100 °C and 120 °C. It was also found that CO and HC emissions firstly increased and then started to decrease after the 90 °C intake air temperature.
Keywords: HCCI gasoline engine; Intake air temperature; Combustion; Auto-ignition timing;
Kinetics of steam gasification of bituminous coals in terms of their use for underground coal gasification by Stanisław Porada; Grzegorz Czerski; Tadeusz Dziok; Przemysław Grzywacz; Dorota Makowska (282-291).
The kinetics of steam gasification was examined for bituminous coals of a low coal rank. The examined coals can be the raw material for underground coal gasification. Measurements were carried out under isothermal conditions at a high pressure of 4 MPa and temperatures of 800, 900, 950, and 1000 °C. Yields of gasification products such as carbon monoxide and carbon dioxide, hydrogen and methane were calculated based on the kinetic curves of formation reactions of these products. Also carbon conversion degrees are presented. Moreover, calculations were made of the kinetic parameters of carbon monoxide and hydrogen formation reaction in the coal gasification process. The parameters obtained during the examinations enable a preliminary assessment of coal for the process of underground coal gasification.
Keywords: High pressure kinetics of coal gasification with steam; Underground coal gasification; Coals for gasification assessment;
Physical and chemical changes of coal during catalytic fluidized bed gasification by David J. Marchand; Erik Schneider; Brian P. Williams; Yong Lak Joo; Jinhong Kim; Gyu Tae Kim; Seong H. Kim (292-298).
Coal gasification was studied by analyzing samples of feedstock extracted from a fluidized bed gasifier at various times throughout the gasification process. The analysis techniques used included energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy for elemental concentrations in the bulk and at the surface, respectively; acidimetric titrations to quantify the concentration of certain oxygen functional groups; and the BET method to determine surface area and porosity. The changes in feed particle size and composition showed that the gasification reaction rate was slow compared to the gas diffusion rates inside the coal particle. Detailed analysis of the composition and oxygen functional groups showed that the catalyst was loaded in the coal by ion exchange with surface oxygen functional groups. As the gasification reaction proceeded, the oxidized carbon content increased in the coal loaded with catalyst, but decreased in the coal without catalyst. That result supports the idea that the catalyst increases the reaction rate by helping to oxidize the carbon and increasing the number of reactive sites, rather than by decreasing the energy barrier for carbon–carbon bond breakage.Display Omitted
Keywords: Coal; Lignite; Gasification; Potassium carbonate; Catalyst; Fluidized bed;
Experimental analysis of biomass co-firing flames in a pulverized fuel swirl burner using a CCD based visualization system by A. González-Cencerrado; B. Peña; A. Gil (299-310).
Biomass co-firing with pulverized coal in conventional, large-scale power plants is considered a low-cost strategy to reduce CO2 emissions and fossil-fuel dependence. This work analyzes the effects of biomass co-firing in the physical characteristics and oscillation patterns of the flame, by means of a digital imaging system installed in a 500 kWth semi-industrial scale swirl burner. The system is based on a monochrome CCD (Charged Couple Device) camera of high-speed frame rate (120 frames per second). Processing stage comprises the digital analysis in the spatial and spectral domain of recorded videos. Several co-firing flames with two biomass fuels (Cynara cardunculus and Populus sp.) were investigated, at substitution percentages ranging from 0% to 15%, energy basis. Spatial analysis of swirling flames highlights the effects of biomass addition in terms of luminous fluctuation rates and symmetry properties. With the joint analysis of flame derived parameters and CO emissions, flame flicker has been proved as a potential indicator of combustion performance. Additionally, a deeper investigation of luminous flame signal throughout its resulting histogram, have found new outcomes in the identification of instabilities of combustion process. Kurtosis and skewness parameters have shown an interesting response when CO emissions increase resulting in a promising option to develop monitoring and control systems based in non-intrusive measurements.Display Omitted
Keywords: Biomass co-firing; Digital image processing; CCD camera; Flame monitoring; Swirl burner; Combustion performance;