Fuel Processing Technology (v.139, #C)
Editorial Board (IFC).
Bio-oil heavy fraction for hydrogen production by iron-based oxygen carrier redox cycle by De-Wang Zeng; Rui Xiao; Shuai Zhang; Hui-Yan Zhang (1-7).
Chemical looping hydrogen generation by the iron-based oxygen carrier redox cycle is promising thanks to its inherent CO2 separation and low energy penalty. Bio-oil heavy fraction, characterized as the oil fraction of pyrolysis bio-oil and difficult to be upgraded for bio-fuel or chemicals production, was used as the feedstock to generate hydrogen for the hydrodeoxygenation process of aqueous phase of pyrolysis bio-oil. The result showed the successful generation of hydrogen by this process, but the undesired carbon formation on the iron-based oxygen carrier resulted in the low purity hydrogen. To avoid this, removal of deposited carbon by the introduction of steam vapor in the fuel reactor was proposed and evaluated. The result confirmed that the positive role of steam vapor played on the enhancement of hydrogen purity, over 99% of hydrogen concentration was obtained in the case of steam to oil ratio at 2.0. However, the hydrogen purity and hydrogen production were in a competing relationship and the hydrogen purity enhancement inevitably suppressed the hydrogen production after steam vapor addition. By taking account of the hydrodeoxygenation process of aqueous phase of pyrolysis bio-oil, the steam to oil ratio of 1.2 was preferred.
Keywords: Bio-oil heavy fraction; Iron-based oxygen carrier redox cycle; Hydrogen production; Hydrogen purity enhancement;
Formation of fireside deposits in feather gasification and heat recovery systems — An industrial case study by Marta Sosnowska; Marek Dudyński; Dariusz Kardaś; Marek Klein; Kamil Kwiatkowski (8-14).
This paper discusses the problem of fireside deposition observed during industrial gasification of feathers in a 3.5 MWth updraft fixed-bed plant equipped with steam boiler. The research included calculating mass balance of the system and performing an analysis of samples of bottom ash and fireside deposits collected from the plant, including XRF, XRD and melting characteristics. Analysis revealed that the bottom ashes and the fireside deposits, collected from the gasification and combustion chambers, consisted of hydroxyapatite with addition of silica and aluminium compounds, while the deposits collected from the boiler and the economiser were formed out of alkali and alkali earth metal sulphates, present in a form of eutectic systems such as 50CaSO4–30K2SO4–20Na2SO4 and 30K2SO4–40Na2SO4–30ZnSO4. The method of minimising fireside deposition by means of additives was discussed and alternative types of boilers suitable for feather gasification systems were proposed as a result of the study.
Keywords: Biomass gasification; Feathers; Syngas; Fixed-bed gasification; Solid deposits;
Effectiveness between swirl intensity and air staging on NOx emissions and burnout characteristics in a pulverized coal fired furnace by Yonmo SUNG; Gyungmin CHOI (15-24).
For opposed wall-fired boilers, the dependency of NOx emission and burnout characteristics on swirl intensity is not straightforward during air-staged combustion. In this study, therefore, influences of swirl vane angle, primary zone stoichiometric ratio, and air staging level on NOx emission and burnout were evaluated experimentally in a laboratory-scale pulverized coal fired furnace. The NOx emission and burnout were a function of residence time in the primary combustion zone. Increasing of the residence time and decreasing of the primary zone stoichiometric ratio had a positive effect on NOx reduction and a negative effect on burnout. There was a tradeoff relationship between the NOx reduction and burnout performance. With controlling of the swirl vane angle, aerodynamic behaviors in the burner region had a strong impact on NOx emissions and burnout characteristics. From the effectiveness analysis of combustion modifications such as the primary zone stoichiometric ratio and swirl vane angle, the control of swirl vane angle was more effective than that in the control of the primary zone stoichiometric ratio. The optimum swirl vane angle should be adjusted with given combustion environments, especially in this research, it was 80°, 45°, and 60° at no staging, air staging level 1, and air staging levels 2–4, respectively.
Keywords: Pulverized coal combustion; Swirl vane angle; Air staging; Burnout; NOx emission;
Factors influencing the Fischer–Tropsch synthesis performance of iron-based catalyst: Iron oxide dispersion, distribution and reducibility by Ren-Jie Liu; Yan Xu; Yu Qiao; Zhen-Hua Li; Xin-Bin Ma (25-32).
The performances of iron-based catalysts supported on SiO2, TiO2 and TS-1 for the Fischer–Tropsch synthesis (FTS) were investigated in a fixed-bed reactor. The results showed that Fe/TS-1 catalyst exhibited better FTS performance than Fe/TiO2 and Fe/SiO2 with higher CO conversion and C5+ selectivity. The desilication treatment of TS-1 further increased the FTS performance of Fe/TS-1 catalyst in terms of activity and stability. These iron-based catalysts were characterized by N2 adsorption, H2 temperature-programmed reduction, X-ray diffraction, transmission electron microscopy, scanning electronic microscopy and thermal gravimetric analysis. The factors influencing the FTS performance of the iron-based catalyst were discussed and the results indicated that not only the dispersion but also the reduction degree of iron oxides increased after desilication treatment of TS-1 support through generating more mesoporous structures and increasing the crystallinity degree of TS-1. The improved FTS activity is due to the increased dispersion of iron particles without affecting the original reducibility. The better stability is due to the enhanced heat and mass transfer as well as the high resistance against coke formation and deposition.
Keywords: Fischer–Tropsch synthesis; Iron catalyst; Dispersion; Distribution; Reducibility;
Deposit build-up and ash behavior in dual fluid bed steam gasification of logging residues in an industrial power plant by Matthias Kuba; Hanbing He; Friedrich Kirnbauer; Dan Boström; Marcus Öhman; Hermann Hofbauer (33-41).
A promising way to substitute fossil fuels for production of electricity, heat, fuels for transportation and synthetic chemicals is biomass steam gasification in a dual fluidized bed (DFB). Using lower-cost feedstock, such as logging residues, instead of stemwood, improves the economic operation. In Senden, near Ulm in Germany, the first plant using logging residues is successfully operated by Stadtwerke Ulm. The major difficulties are slagging and deposit build-up. This paper characterizes inorganic components of ash forming matter and draws conclusions regarding mechanisms of deposit build-up. Olivine is used as bed material. Impurities, e.g., quartz, brought into the fluidized bed with the feedstock play a critical role. Interaction with biomass ash leads to formation of potassium silicates, decreasing the melting temperature. Recirculation of coarse ash back into combustion leads to enrichment of critical fragments. Improving the management of inorganic streams and controlling temperature levels is essential for operation with logging residues.
Keywords: Biomass gasification; Deposit build-up; Olivine; Bed material agglomeration; Logging residues;
Ozone as oxidation agent in cyclic activation of biochar by Diana Jimenez-Cordero; Francisco Heras; Noelia Alonso-Morales; Miguel A. Gilarranz; Juan J. Rodriguez (42-48).
Granular activated carbons were produced from grape seed biochar by cyclic activation with ozone. In each cycle, char was first oxidized by exposure to ozone and then subjected to high temperature in inert atmosphere to desorb oxygen groups formed. The study assessed the influence of operating conditions in the development of porosity, from a starting biochar with narrow microporosity (S BET: 47 m2 g− 1, SDA: 505 m2 g− 1) prepared by flash pyrolysis of grape seed at 800 °C. The variables studied were the number of cycles applied and the oxidation and desorption temperatures (250–275 and 850–950 °C, respectively). High oxidation temperatures led to higher burn-off, which was also found to increase with the number of activation cycles. The burn-off needed to achieve a high surface area was lower than in conventional physical activation. After 7–9 activation cycles, activated carbons with S BET higher than 1200 m2 g− 1 and S DA above 1500 m2 g− 1 were obtained. The use of ozone resulted in mainly microporous activated carbons (0.37–0.52 cm3 g− 1) with very low contribution of mesopores (< 0.04–0.07 cm3 g− 1). The mean micropore size increased with the number of activation cycles due to pore widening, while mesopore mean size decreased along the cycles. The activated carbons showed a unique granular morphology with a hollow core and a porous shell, which is maintained even after 10 activation cycles.
Keywords: Biochar; Granular activated carbons; Grape seed; Activation; Ozone;
Use of zeolites for the removal of H2S: A mini-review by Mehtap Ozekmekci; Gozde Salkic; Mehmet Ferdi Fellah (49-60).
Being a successful adsorbent for removal of hydrogen sulfide, zeolites should have good sulfur loading capacity, good regenerability and stable structure. These are natural zeolites having high adsorption capacity compared to other zeolites and synthetic zeolites. Zeolites can be modified by metals or metal oxides in order to increase their adsorption capacity. Removal of H2S is an essential process because it leads to corrosion in transport lines and poisoning of many catalysts even in low levels. Different types of adsorption methods such as fixed bed adsorption, pressure swing adsorption and sequential bed methods were experimentally used to investigate the removal of hydrogen sulfide. Computational methods (DFT) were also utilized theoretically. ETS-2 zeolite can be good choice to remove H2S due to its adsorbent properties. However this material has not been studied so much. Therefore more studies should be done experimentally and theoretically to examine the removal of hydrogen sulfide on excellent metal exchange forms of ETS-2. Consequently zeolites that have sulfur capacity increasing with modifications of metals or metal oxides are promising materials due to their high surface–volume ratio which is one of the most important factors in adsorption.Display Omitted
Keywords: H2S; Hydrogen sulfide; Removal; Zeolite;
Spectroscopic analysis of crude rapeseed oil flame by Viktor Józsa; Attila Kun-Balog (61-66).
Utilizing crude vegetable oils in all types of heat engines can be a part of a sustainable economy in the future. Focusing on their local usage, they can possibly compete with fossil fuels. Furthermore, to keep the pollutant emissions at the lowest possible level, the feedback control of the equivalence ratio is essential. Regarding the harsh environment of the combustion chambers, optical flame diagnostics is a potential tool. Therefore, in order to examine its feasibility, the comparison of flame emission spectroscopy (FES) of rapeseed oil with standard diesel oil was carried out at atmospheric conditions in a lean premixed prevaporized (LPP) burner at 15 kW of firing power. The well-known chemiluminescence intensity ratios of OH*, CH*, and C2* at 516 nm (C2, 516*) were investigated. A further significant peak was found at 554 nm in case of rapeseed oil firing, which probably corresponds to C2* (C2, 554*). The corrected chemiluminescence intensity ratios as a function of air–fuel equivalence ratio are shown in the current work. It was found that these ratios involving C2* at either 516 or 554 nm show less sensitivity to the pressure of atomizing air than OH*/CH*, therefore they are more suitable for diagnostics and for the control of the equivalence ratio of liquid fired burners.
Keywords: Flame emission spectroscopy; OH chemiluminescence; CH chemiluminescence; Rapeseed oil; Pollutant emission; Gas turbine;
Combustion characteristics, performance and emissions from a diesel power generator fuelled by B7-ethanol blends by Alex de Oliveira; André Marcelino de Morais; Osmano Souza Valente; José Ricardo Sodré (67-72).
The effects of fuel blends containing 5, 10 and 15 wt.% of anhydrous ethanol in diesel oil with 7% of biodiesel (B7) on performance, emissions and combustion characteristics of a diesel power generator are investigated. The engine was tested with its original configuration, with the fuel blends directly injected into the combustion chamber, and the applied load varied from 5 to 37.5 kW. The results were compared with standard B7 operation, and showed that in in-cylinder peak pressure and heat release rate were decreased at low loads and increased at high loads with the use of ethanol. Increasing ethanol concentration caused increased ignition delay, decreased combustion duration and reduced exhaust gas temperature. The use of ethanol decreased carbon dioxide (CO2) emissions, up to 8.6% lower than B7. Carbon monoxide (CO), total hydrocarbons (THC) and oxides of nitrogen (NOX) emissions showed different behavior, depending on load and ethanol concentration.
Keywords: Ethanol; Diesel engine; Combustion; Emissions; Power generation;
A generalized model of SO2 emissions from large- and small-scale CFB boilers by artificial neural network approach Part 2. SO2 emissions from large- and pilot-scale CFB boilers in O2/N2, O2/CO2 and O2/RFG combustion atmospheres by J. Krzywanski; T. Czakiert; A. Blaszczuk; R. Rajczyk; W. Muskala; W. Nowak (73-85).
Since sulfur release and capture processes during solid fuel combustion in circulating fluidized bed (CFB), especially in oxy-fuel conditions are very complex, the development of a simple SO2 emissions model for a wide range of operating conditions both for large- and pilot-scale boilers is of practical significance.Previously established and validated [16-1-6-1] ANN model, which was published in the Part 1 of this paper was employed to predict SO2 emissions from coal combustion in a large-scale 261 MWe CFB COMPACT-type boiler as well as in a pilot-scale 0.1 MWth OxyFuel–CFB test rig.The simulations are carried out using artificial neural network approach for different combustion environments, both in atmospheric and pressurized conditions. The study is conducted for air-firing, oxygen-enriched and oxy-fired combustion conditions. Therefore, four different combustion atmospheres are considered in the paper, where combustion runs in air and air enriched with oxygen (O2/N2 mode) as well as in oxycombustion (oxygen-fired combustion) conditions, which mean the mixture of oxygen with CO2 or recycled flue gas (RFG) with various fractions of oxygen (O2/CO2 mode and O2/RFG mode, respectively).The obtained results show that the ANN model makes it possible to predict the SO2 emissions from coal combustion in CFB boilers of different sizes and in different combustion environments.
Keywords: Oxy-combustion; CFB boilers; Desulfurization; Pressurized combustion; Artificial neural networks; Modeling;
Production of C2 and C3 polyols from d-sorbitol over hydrotalcite-like compounds mediated bi-functional Ni–Mg–Al–Ox catalysts by Wei-Chen Du; Li-Ping Zheng; Juan-Juan Shi; Shui-Xin Xia; Zhao-Yin Hou (86-90).
Production of C2 and C3 polyols from d-sorbitol over Ni/MgxAlyOx + 1.5y catalysts with different Mg/Al molar ratio were performed under mild conditions. It was found that this reaction proceeded effectively over these bi-functional catalysts prepared via thermal decomposition and reduction of Ni–Mg–Al hydrotalcite-like compounds. The detected conversion of d-sorbitol over Ni/Mg1.29Al0.06O1.38 reached 80.7% at 453 K and further increased to 97.0% at 473 K. Characterizations indicate that the performance of these catalysts depended mainly on its surface basicity.Display Omitted
Keywords: d-Sorbitol; Hydrogenolysis; Ni catalyst; Surface basicity;
Study on palm oil hydrogenation for clean fuel over Ni–Mo–W/γ-Al2O3–ZSM-5 catalyst by Hong-Yan Wang; Tian-Tian Jiao; Zeng-Xi Li; Chun-Shan Li; Suo-Jiang Zhang; Jian-Ling Zhang (91-99).
Biodiesel, derived from vegetable oil via hydrotreating, is becoming a promising alternative energy. Novel Ni–Mo–W/γ-Al2O3–ZSM-5 catalysts were developed and firstly applied in palm oil hydrogenation process. The catalysts were prepared by extrusion method and characterized by XRD, SEM, TEM, BET, NH3–TPD, and H2–TPR. The influences of acidity on the activity, selectivity, and stability of catalysts were systematically studied. The mechanisms of deoxygenation and isomerization were discussed. The catalyst Ni–Mo–W (5 wt.%–5 wt.%–15 wt.%)/γ-Al2O3–ZSM-5 (85 wt.% − 15 wt.%) was confirmed as the optimum one. Finally, the key reaction parameters such as reaction temperature, pressure, liquid hourly space velocity and H2/oil volume ratio were optimized. The hydrogenation reaction path of palm oil was also proposed.
Keywords: Hydrogenation; Palm oil; Biodiesel; Cetane number;
Examination of the effects of organic based manganese fuel additive on combustion and engine performance by Mehmet Çelik; Hamit Solmaz; H. Serdar Yücesu (100-107).
The physical and chemical properties of the fuel used in internal combustion engines affect fuel economy and emission characteristics. Various additives are added into diesel fuel in order to improve fuel quality, achieve better combustion and reduce exhaust emissions. Acting as catalyzers during combustion, additives expedite fuel instability reactions and establish positive effects on engine performance. In the present study organic based manganese additive was added into diesel fuel. Combustion, performance and exhaust emission characteristics of the manganese fuel additives were investigated. The tests were carried out in a single-cylinder diesel engine. Among the fuels supplemented with organic based manganese additive, the best results were obtained from 12 ppm mixture rate. In comparison with diesel fuel, the maximum power of the D0Mn12 fuel increased by 12.48% while the specific fuel consumption was reduced by 8.17%. At fuel load while CO, THC and smoke emissions were determined to remain at the minimum levels in the fuel D0Mn12, NOx emissions reached the maximum level.
Keywords: Diesel engines; Fuel additives; Manganese; Combustion characteristics; Exhaust emissions; Motor performance;
Modeling study of oil shale pyrolysis in rotary drum reactor by solid heat carrier by Gennady Gerasimov; Eduard Volkov (108-116).
The mathematic model of oil shale thermal decomposition (pyrolysis) was constructed on the base of analysis of available experimental data. The model was applied to the engineering procedure that simulates the Galoter process, namely, pyrolysis of oil shale in a horizontal rotary drum reactor in contact with fine-grained solid heat carrier (hot ash). The model includes the kinetics of organic matter (kerogen) decomposition, the processes of heat and mass transfer inside of single oil shale particle, polydispersity of the particles, their fragmentation, and the secondary chemical reactions such as the carbonization of the emitted shale oil on the ash particles as well as shale oil decomposition the free volume of the reactor. Calculations show that the secondary reactions lead to reduce the shale oil yield from 0.27 to 0.13 kg/kg of dry shale, what is close to operating data of the various industrial units based on the Galoter technology.
Keywords: Oil shale pyrolysis; Mathematic model; Galoter process; Rotary drum reactor; Heat and mass transfer; Decomposition kinetics;
Catalytic cracking of camelina oil for hydrocarbon biofuel over ZSM-5-Zn catalyst by Xianhui Zhao; Lin Wei; Shouyun Cheng; Yinbin Huang; Yong Yu; James Julson (117-126).
Cracking of camelina oil over non-catalyst and ZSM-5 catalyst doped with different Zn concentrations (0, 10, 20 and 30 wt.%) in a fixed-bed reactor was investigated. The fresh and used catalysts were characterized using XRD, FT-IR, BET and TEM. Characterizations of the produced hydrocarbon biofuel, distillation residual and non-condensable gas were carried out. The effect of non-catalyst and catalyst on the physicochemical properties and yield of products was discussed. The results showed that the introduction of Zn did not change the zeolite crystalline structure and ZnO might deposit on the external surface and/or inside the pores of the support ZSM-5. After upgrading, hydrocarbon biofuel had a lower viscosity, lower density, higher heating value (HHV) and higher water content than raw camelina oil. The optimum Zn concentration to ZSM-5 was 20 wt.%, at which the highest hydrocarbon biofuel yield and comprehensively the best quality were obtained. Compared to non-catalytic cracking of camelina oil, the loading of Zn to ZSM-5 could improve some physicochemical properties of the hydrocarbon biofuel. In addition, the loading of Zn to ZSM-5 could facilitate the chemical reactions such as decarbonylation and dehydrogenation.
Keywords: Catalytic cracking; Camelina oil; Biofuel; ZSM-5-Zn; Gas;
Enhancing fuel qualities of cassava crop residues by washing by Björn Hedman; Dan Boström; Wanbin Zhu; Håkan Örberg; Shaojun Xiong (127-134).
Cassava (Manihot esculenta Crantz) stems, being waste residues after harvesting starchy roots, are a potential biofuel resource. However high concentrations of ash and elements Cl, K, etc. in the stems may cause severe deposition, corrosion and particle emissions, in addition to slagging during combustion. This study tests washing by water as a pretreatment to reduce the problems. A 3-level full factorial designed experiment was conducted with washing time (< 1800 s) and temperature (20–40 °C) as factors and fuel characteristics as responses. The effect of milling particle size was also examined in a supplementary experiment.After washing, the net calorific value of the biomass tended to be higher, though not significant. Both washing time and temperature increased C but decreased H, while N and S content decreased with time only. A short washing of 50 s decreased the ash content by approximately 50% and Cl around 75%, followed by K and P that decreased to 50% after 5 min. Smaller milling size resulted in a larger amount of starch washed away, but no significant change in content of total ash and individual elements, except for Cl which was significantly higher in the smaller particles. The effect of washing on the ash composition is visualized in a ternary diagram, showing that the risk for slagging and fine particle emissions is reduced. A reduction in the risk of corrosion is also predicted as indicated by a relatively higher ratio of S/Cl and lower Cl/(K + Na). Thus, in addition to extraction of starch, the washing can also improve fuel quality of the residual biomass.
Keywords: Biomass property; Biomass refining; Ash composition; Thermal conversion; Chlorine; Potassium;
Characterization of the properties of diesel-base oil-solvent-waste oil blends used as generic fuel in diesel engines by Kadir Gedik; Yasin Uzun (135-141).
Foreign-dependent pricing policy in petroleum sector has led the market opportunists and transportation sector drivers to seek alternative cheaper fuels for diesel engines in Turkey. A new generic fuel blend of virgin/nonstandard base oils and/or low taxation wastes (waste lubricants, mineral oils, heavy solvent formulations etc.) with diesel fuel called number 10 lube (NTL) has been widely used for such purposes in public transportation vehicles or trucks over the last decade. Therefore, this study was conducted to characterize the fuel properties of NTLs to evaluate the probable impacts on engine performance and exhaust emissions. All tests (density, viscosity, flash point, pour point, water content, sulfur content, volatile content, acid number, base number, corrosiveness, color and Fourier Transform Infrared Spectroscopy analysis) were conducted at an accredited fuel analysis laboratory. The results showed a large fluctuation in NTL properties among the dealers or location. The outlier values observed for various physicochemical parameters indicated adulteration with different types of waste oils (vegetable, cooking, engine, mineral) and solvents in NTLs which make them unsuitable for diesel engines. Such an adulteration case is exceptional but fuel misuse is a common problem in the world, hence, should be managed properly and tackled with implementation of appropriate taxes.
Keywords: Crude oil; Number 10 lube; Physicochemical properties; Fuel adulteration; FTIR;
Development and validation of CFD models for gas phase reactions in biomass grate furnaces considering gas streak formation above the packed bed by Ali Shiehnejadhesar; Robert Scharler; Ramin Mehrabian; Ingwald Obernberger (142-158).
State-of-the-art packed bed models supply continuous concentration profiles as boundary conditions for subsequent CFD simulations of gas phase, leading to pre-mixed combustion conditions. However, in reality the “porous” nature of the packed bed leads to streak formation influencing gas mixing and combustion. Therefore, in the present work, in order to account for the influence of the streaks on gas phase combustion, a gas streak model based on a correlation between the local gas residence time and a mixing time has been developed based on numerical simulations. Finally, the streak model was linked with an in-housed developed hybrid gas phase combustion model suitable for laminar to highly turbulent flow conditions and applied for an under-feed pellet stoker furnace (20 kWth) concerning the simulation of gas phase combustion and NOx formation. The results in comparison with a simulation without the streak formation model show that the flue gas species prediction can be improved with the proposed streak formation model. Especially, in the region above the fuel bed (in the primary combustion chamber), this is of special importance for NOx reduction by primary measures.
Keywords: CFD modelling; Biomass; Combustion; Grate furnace; Streak formation model; Hybrid model;
Mechanical dewatering and water leaching pretreatment of fresh banagrass, guinea grass, energy cane, and sugar cane: Characterization of fuel properties and byproduct streams by Hong Cui; Scott Q. Turn; Thai Tran; Daniel Rogers (159-172).
Tropical biomass feedstock candidates, banagrass (Pennisetum purpureum × Pennisetum glaucum), guinea grass (Panicum maximum), energy cane (Saccharum spontaneum), and sugar cane (Saccharum officinarum L.) (as reference) were harvested and processed using pressing and leaching techniques to improve fuel properties for thermochemical conversion. Test results are reported that summarize the impacts of treatment methods on fuel properties and provide detailed data on mass and element partitioning between process streams to inform system design. The processed fuels had lower ash contents, improved heating values, higher ash deformation temperatures, and higher volatile matter to fixed carbon ratios than the parent materials. The liquid streams generated by the process were characterized for chemical oxygen demand, sugar content, total solids, total suspended solids, and major and trace elements. At least 20% of the initial fuel dry matter was partitioned to the byproduct liquid streams as total solids under the combined influences of leaching and mechanical processing. Analytical results support the land application of liquids as a nutrient recycling option. Element partitioning between solid and liquid process streams was determined and material and element mass balances were performed. Chemical equilibrium calculations based on the elemental composition of the parent materials and processed fuels and steam gasification conditions predicted substantial reductions in concentrations of K, Cl, S, Na, and Mg in the product gas.Fuel processing for fresh biomass feedstock to improve fuel properties for thermochemical conversion.Display Omitted
Keywords: Fresh biomass; Fuel processing; Fuel properties; Waste liquids analysis; Inorganic impurity elements; Trace elements; Thermochemical conversion;
Large-scale synthesis and catalysis of oleic acid-coated Fe2O3 for co-liquefaction of coal and petroleum vacuum residues by Zhi-Qiang Sun; Feng-Yun Ma; Xue-Jiao Liu; Hang-Hang Wu; Chun-Ge Niu; Xin-Tai Su; Jing-Mei Liu (173-177).
Two kinds of well-dispersed oleic acid-coated Fe2O3 nanoparticles (NPs) were prepared using hydrothermal method as catalysts I and II in milligram- and gram-scales, respectively. According to analyses with X-ray diffraction and transmission electron microscopy, the two kinds of NPs are nearly spherical with diameters of ca. 5 and 8 nm for milligram- and gram-scale preparations, respectively. The results of co-liquefaction of coal and petroleum vacuum residue (PVR) show that catalysts I and II exhibit better activity than Fe2O3 and no catalyst under the same conditions carried in a 100 mL batch reactor. Specifically, the soluble portion (SP) yield is beyond 92% over Fe2O3, catalyst I or II, whereas the one is only 85% without catalyst. The total oil yields are 82.83% and 83.67% over catalysts I and II, respectively, whereas 74.69% and 70.35% over Fe2O3 and no catalyst, respectively. According to analysis with simulated distillation, diesel and gasoline yields over catalysts I and II increased compared to no catalyst.Display Omitted
Keywords: Oleic acid-coated Fe2O3; Catalyst; Gram scale; Co-liquefaction;
Ethanol purification from methanol via pervaporation using polybеnzoхazinonеimidе membrane by Alexandra Yu. Pulyalinа; Galina A. Polotskaya; Кseniya Yu. Veremeychik; Mikhail Ya. Goikhman; Irina V. Podeshvo; Alexander M. Toikka (178-185).
Polybenzoxazinoneimide membrane was prepared in three steps: a dichlorodianhydride (obtained by the reaction of trimellitic anhydride with 4,4′-oxydianiline) was treated with methylene-bis(anthranilic acid). The resulting polyamic acid was dissolved in N-methylpyrrolidone, the solution was cast as a thin film, the solvent was evaporated and the membrane was heated under controlled conditions to convert polyamic acid into polybenzoxazinoneimide. Density, free volume parameters, sorption parameters for methanol and ethanol of the membrane were determined. The membrane was used for the pervaporation of methanol/ethanol mixtures containing 5–20 wt.% methanol which are mixtures modeling bioalcohol. The membrane was preferentially permeated by methanol with high separation factors.Display Omitted
Keywords: Biofuel; Methanol/ethanol separation; Pervaporation; Polybenzoxazinoneimide;
Conceptual design of an autonomous once-through gas-to-liquid process — Comparison between fixed bed and microchannel reactors by Mohammad Ostadi; Kristin Dalane; Erling Rytter; Magne Hillestad (186-195).
A novel process concept is proposed for converting natural gas to liquid Fischer–Tropsch products. An autothermal reformer with enriched air as oxidant is applied for synthesis gas (syngas) production, and because of the inert nitrogen a once-through Fischer–Tropsch synthesis is the preferred option. In order to maximize the syngas conversion and the production of heavy hydrocarbons, a staged reactor path with distributed hydrogen feed and product withdraw is proposed. The hydrogen is produced by steam methane reforming in a heat exchange reformer (gas heated reformer), heat integrated with the hot effluent stream from the autothermal reformer. Tail gas from the last Fischer–Tropsch stage is sent to a gas turbine for power production. The hot exhaust gas from the gas turbine is used for natural gas preheating. The process is autonomous in the sense that it is self sufficient with power and water, and therefore well suited for production in remote locations such as a floating production unit. The process concept is simple and inexpensive since cryogenic air separation and fired heaters are not required. For the Fisher–Tropsch synthesis, both the conventional shell and tube fixed bed reactors and microchannel reactors are considered and compared.
Keywords: Gas-to-liquid; Fischer–Tropsch; Autothermal reformer; Heat exchange reformer; Fixed bed reactor; Microchannel reactor; Distributed hydrogen feed; Autonomous; FPSO; Remote gas;
Anthracite oxy-combustion characteristics in a 90 kWth fluidized bed reactor by Luis I. Díez; Carlos Lupiáñez; Isabel Guedea; Irene Bolea; Luis M. Romeo (196-203).
A comprehensive experimental characterization of Spanish anthracite oxy-combustion has been conducted, and the results are discussed in this paper, encompassing combustion efficiency, heat transfer, and pollutant emissions. The experimental work has been carried out in a 90 kWth bubbling fluidized reactor under a variety of O2/CO2 atmospheres and operating conditions (fluidization velocity, Ca:S ratio, and secondary oxidant supply). Combustion efficiency is improved under oxy-firing compared to air-firing, mainly due to the multiple-bubble regime and the lower fluidization velocities. The share of radiative heat transfer also rises, since O2/CO2 operation leads to an increase of the temperature in the dense zone of the reactor. Concerning SO2 emissions, the minimum values are found under the richest O2 atmosphere, yielding maximum values of sulfur capture efficiency in the temperature range of 880–890 °C. A decrease of NOx emissions is also observed under oxy-firing conditions, while the benefit of secondary oxidant supply has to be optimized for every specific O2 concentration.
Keywords: Oxy-combustion; Anthracite; Fluidized bed reactors; Heat transfer; SO2 and NOx emissions;
Characterization and density separation of coal gasification residues generated from the Zecomix research infrastructure by Milena Morone; Giulia Costa; Stefano Stendardo; Renato Baciocchi (204-215).
This paper presents the results of characterization investigations carried out on the solid residues produced during coal gasification tests performed in the Zecomix (Zero Emission of CarbOn with MIXed technology) research infrastructure. In this pilot-scale plant, coal is gasified in a steam/oxygen-blown bubbling fluidized bed containing olivine. The solid residues, collected both directly from the solid bed (bed ash) and downstream from it (mixed ash), were characterized in terms of their main physical, chemical and mineralogical properties with the aim of identifying suitable management strategies for each of them within the Zecomix process. Thus, an experimental protocol was also developed to separate the organic and inorganic fractions of both ash types. The main constituents of the bed ash were Mg, Si and Fe, which represent the elemental components of olivine. The total organic carbon content of the bulk bed ash was of 5%, while that of the bulk mixed ash proved to be significantly higher (24–27%). Finally, the particle size and density separation procedure developed in this work showed to be effective for separating the organic and inorganic fractions of the bulk samples of both types of residues, allowing to reach separation efficiencies higher than 90%.
Keywords: Coal gasification; Ash; Mineralogy; Density separation;
Evaluation of black liquor gasification intended for synthetic fuel or power production by Henrik Wiinikka; Ann-Christine Johansson; Jonas Wennebro; Per Carlsson; Olov G.W. Öhrman (216-225).
The performance of a high-temperature pressurized black liquor gasifier intended for fuel or power production was evaluated both by thermochemical equilibrium calculations and with experiments performed in a development plant with a maximum capacity corresponding to 3 MWth. The aim of this paper was to investigate how the energy efficiency and the performance of the gasifier change with desired use of the syngas and to provide an accurate process analysis which can be used in future work for process optimization and understanding. Experiments in the plant were performed for an oxygen equivalence ratio (λ) between 0.414–0.462 at two system pressures, 24.6 and 28.7 bar, respectively. The thermal load on the gasifier was 2.7 MWth during the experiments.The experimentally verified cold gas efficiency taking into account all gaseous species varied between 59.0–62.4%. However, if only CO and H2 (which are the effective molecules for synthetic fuel production) were taken into account; the cold gas efficiency decreased considerably to 53.7–55.4% due to the presence of CH4 in the gas. The results indicate that optimal performance for synthetic fuel production occurs at a higher λ compared to power production. There is also a potential to further improve the performance for an optimal operated commercial plant in the future since the theoretical results indicate that the cold gas efficiency could be as high as 68.8% (λ = 0.35) for fuel production and 81.7% (λ = 0.27) for power production.
Keywords: Biomass; Black liquor; Gasification; Biofuel production; Power production;
Detailed identification and quantification of the condensable species released during torrefaction of lignocellulosic biomasses by Kim Lê Thành; Jean-Michel Commandré; Jérémy Valette; Ghislaine Volle; Michel Meyer (226-235).
Torrefaction is a mild thermal pretreatment which improves biomass properties and releases condensable species. Condensable species released during torrefaction of pine, ash wood, miscanthus and wheat straw at 250, 280 and 300 °C were investigated. A fixed-bed reactor was used for the laboratory scale experiments. A micro-GC, Karl Fischer titrator and GC-MS were used to analyse incondensable gases, water and other condensable species, respectively. The overall mass balance ranged from 96 to 103 wt.%. The quantification rate of condensable species was on average 77 wt.%. In addition to the major species usually reported in the literature – water, acetic acid, 2-propanone,1-hydroxy- – we show that large amounts of some anhydrosugars were produced. Additionally, 85 condensable species were identified. Among these species, many terpenes and terpenoids in pine were identified by adsorption on SPME fibre. Finally, the influence of temperature and of the nature of biomass on the yields of condensable species was highlighted.
Keywords: Lignocellulosic biomass; Torrefaction; Mild pyrolysis; Volatiles; Condensable species; Gas analysis; GC–MS; Adsorption;
Studies on carbon flotation from fly ash by Wencai Zhang; Rick Honaker (236-241).
The separation of carbon from fly ash significantly improves the potential end-us of combustion byproducts. Froth flotation is the most effective separation technique for ultrafine material. Diesel dosages, conditioning time, and impeller rotating speeds' influences on carbon flotation performance were studied. From flotation products, + 25 and − 25 μm fractions were screened out to study their different flotation behaviors. At a given impeller speed, carbon recovery of +25 μm fraction increased significantly from 38.46% to 74.22% over a range of diesel dosage from 0.5 to 4.5 kg/t, while that of -25 μm fraction was relatively constant at 85% over the same diesel dosage range. Morphologies and microstructures of coarse and fine carbon were studied by using scanning electron microscope. Porous structures of coarse carbon were observed. It's difficult for diesel droplets of several microns to penetrate the pores of coarse carbon particles, which increases diesel consumption. Increasing impeller speeds from 1200 to 1600 rpm during conditioning improved the carbon recovery and separation efficiency of + 25 μm fraction by 79% and 110%, respectively, which significantly reduced diesel consumption. Flotation kinetic studies indicate that increasing impeller speeds during conditioning stage can improve the flotation rate constant and maximum carbon recovery for both + 25 and − 25 μm fractions.
Keywords: Fly ash; Carbon; Separation; Flotation;
Efficiency testing of three biogas siloxane removal systems in the presence of D5, D6, limonene and toluene by Tuula Kajolinna; Päivi Aakko-Saksa; Johannes Roine; Leif Kåll (242-247).
Increasing utilization of biogas as an energy source sets various design requirements for gas quality and gas cleaning systems. This study presents efficiency tests for three different siloxane removal systems: activated carbon, silica gel and molecular sieve based systems. Tests were performed in a nitrogen matrix. The injected impurities were siloxane compounds (D5, D6), limonene and toluene. The activated carbon and molecular sieve systems had the highest siloxane removal efficiencies in these tests. Silica gel media also had a good siloxane removal efficiency, and it was more selective in the removal of siloxanes than the other systems.Display Omitted
Keywords: Biogas; Purification; Siloxane;
Texture, acidity and fluid catalytic cracking performance of hierarchical faujasite zeolite prepared by an amphiphilic organosilane by Christiaan H.L. Tempelman; Xiaochun Zhu; Kristina Gudun; Brahim Mezari; Baojian Shen; Emiel J.M. Hensen (248-258).
Mesoporous zeolite Y was synthesized by using an amphiphilic organosilane. The texture and acidity of the mesoporous zeolite samples were compared with a reference microporous faujasite zeolite. The synthesis of the most suitable mesoporous zeolite Y was scaled up in order to prepare composite catalysts that could be tested for fluid catalytic cracking. Composite catalysts were prepared by spray-drying the zeolite with kaolin as filler and an alumina sol as binder. The acidic properties of composite FCC catalysts prepared from conventional and mesoporous faujasite zeolites were compared. While IR spectroscopy after H/D exchange with deuterated benzene indicates that strong bridging hydroxyl groups are present in the freshly prepared composite catalysts, these zeolite-type acid sites are absent in the lab-deactivated composite catalysts. These samples contain a significant number of weaker Brønsted acid sites. The strength of the acid sites in the composite catalysts is comparable with the acidity of amorphous silica–alumina. The composite catalysts show an excellent catalytic performance in the fluid catalytic cracking of vacuum gas oil. Our data indicate that relatively weak acid sites catalyze the FCC reactions. The well-embedded mesoporosity in the parent hierarchical zeolite crystals results in increased diesel and decreased gasoline and coke yield in the composite FCC catalyst.Display Omitted
Keywords: Zeolites; Faujasite; Fluid catalytic cracking; Mesoporosity; Acidity; Yield;