Sorptive storage of natural gas onto dry and wet phillipsite: Study of dynamics,storage and delivery

In this work, storage of methane on phillipsite, a naturally occurring zeolite, was studied on wet and dry basis. The temperature and pressure dynamics were investigated. The temperature gradient due to the adsorption of methane on phillipsite was less than 1 °C indicating higher thermal conductivity of this material. A decreased in temperature resulted in higher adsorption capacity. Storage of methane onto phillipsite can be enhanced by wetting the bed and thus hydrate formation. The time needed to reach equilibrium depends strongly on the water content of the adsorbent. The results revealed that the total delivery capacities for dry and wet phillipsite were 32.5 V/V and 74.13 V/V, respectively. A maximum delivery capacity of 138 V/V was reached using wet phillipsite with 350 g water content. The volumetric delivery capacity results indicated that the steady state delivery is more realistic for adsorptive natural gas (ANG) systems.     

Preparation,characterization and electrolytic behavior of β-nickel hydroxide

Nickel hydroxide is prepared by neutralizing NiSO₄ solution with 4.8 M NaOH, followed by washing the precipitate and treating the slurry hydrothermally at different temperatures. The parameters varied are: initial nickel concentration; effect of presence of sodium ions during hydrothermal treatment; aging time after hydrothermal treatment. The samples so prepared are chemically analyzed and the physical and electrolytic properties such as tap density, percentage weight loss and discharge capacity are determined. On increasing the temperature from 60 to 160 °C, the discharge capacity increases from 52 to 112 mAh g⁻¹. At 200 °C, the discharge capacity decreases to 94 mAh g⁻¹. Allowing the hydroxide precipitate to age after hydrothermal treatment also causes a decrease in discharge capacity. The presence of excess sodium ions during hydrothermal treatment yields nickel hydroxide with a very low discharge capacity. The maximum discharge capacity of 160 mAh g⁻¹ is obtained for nickel hydroxide prepared under the following conditions: nickel concentration 43 g l⁻¹, neutralizing agent sodium hydroxide, time of hydrothermal treatment 2 h, temperature during hydrothermal treatment 160 °C. XRD patterns and FTIR spectra confirm the precipitate to be β-nickel hydroxide. The sample contains 62.89 wt.% Ni with a tap density of 0.96 g cm⁻³. TG–DTA measurements show a weight loss of 19% with an endothermic peak at 325 °C which corresponds to the decomposition of nickel hydroxide to nickel oxide. The present method of preparing nickel hydroxide through hydrothermal treatment reduces the aging time to 2 h and gives a product with good filtration characteristics.     

Optimization of ethanol production from sweet sorghum (Sorghum bicolor) juice using response surface methodology

Sweet sorghum juice was fermented into ethanol using Saccharomyces cerevisiae (ATCC 24858). Factorial experimental design, regression analysis and response surface method were used to analyze the effects of the process parameters including juice solid concentration from 6.5 to 26% (by mass), yeast load from 0.5 g L⁻¹ to 2 g L⁻¹ and fermentation temperature from 30 °C to 40 °C on the ethanol yield, final ethanol concentration and fermentation kinetics. The fermentation temperature, which had no significant effect on the ethanol yield and final ethanol concentration, could be set at 35 °C to achieve the maximum fermentation rate. The yeast load, which had no significant effect on the final ethanol concentration and fermentation rate, could be set at 1 g L⁻¹ to achieve the maximum ethanol yield. The juice solid concentration had significant inverse effects on the ethanol yield and final ethanol concentration but a slight effect on the fermentation rate. The raw juice at a solid concentration of 13% (by mass) could be directly used during fermentation. At the fermentation temperature of 35 °C, yeast solid concentration of 1 g L⁻¹ and juice solid concentration of 13%, the predicted ethanol yield was 101.1% and the predicted final ethanol concentration was 49.48 g L⁻¹ after 72 h fermentation. Under this fermentation condition, the modified Gompertz's equation could be used to predict the fermentation kinetics. The predicted maximum ethanol generation rate was 2.37 g L⁻¹ h⁻¹.     

On thermodynamics of methane + carbonaceous materials adsorption

This study presents the theoretical frameworks for the thermodynamic quantities namely the heat of adsorption, specific heat capacity, entropy, and enthalpy for the adsorption of methane onto various carbonaceous materials. The proposed theoretical frameworks are developed from the rigor of thermodynamic property surfaces of a single component adsorbate–adsorbent system and by incorporating the micropore filling theory approach, where the effect of adsorbed phase volume is considered. The abovementioned thermodynamic properties are quantitatively evaluated from the experimental uptake data for methane adsorption onto activated carbons such as Maxsorb III at temperatures ranging from 120 to 350 K and pressures up to 25 bar. Employing the proposed thermodynamic approaches, this paper shows the thermodynamic maps of the charge and discharge processes of adsorbed natural gas (ANG) storage system for understanding the behaviors of natural gas in ANG vessel.     

Performance of a polyaniline(DMcT)/carbon fiber composite as cathode for rechargeable lithium batteries

The redox reaction of 2,5-dimercapto-1,3,4-thiadiazole (DMcT) is slow at room temperature, but it can be accelerated when the electron transfer reaction is coupled with that of polyaniline (Pani). Films of polyaniline were electrosynthesized onto carbon fiber substrates by cyclic voltammetry from a 0.5 mol L⁻¹ H₂SO₄/0.1 mol L⁻¹ aniline aqueous solution; DMcT was incorporated into the films by two different procedures: A – previous adsorption on the carbon fiber substrate, and B – electropolymerization onto a Pani film from a 20 mmol L⁻¹ DMcT solution in acetonitrile. The Pani(DMcT)/carbon fiber composites were tested as cathodes at 0.1 mA cm⁻² in a cell containing lithium as anode in a 0.5 mol L⁻¹ LiClO₄ solution in propylene carbonate, in a dry box under an argon atmosphere at 25 ± 2 °C. Discharge capacity values of 159 mA h g⁻¹ (after 90 cycles) and 39 mA h g⁻¹ (after 50 cycles) were obtained for the composites prepared by procedures A and B, respectively. The high capacity value and the high electrochemical stability during the cycling indicate that there is a synergetic effect of Pani and DMcT in the composites prepared by procedure A.     

Implementation of an UASB anaerobic digester at bagasse-based pulp and paper industry

Upflow anaerobic sludge blanket (UASB) reactor was installed to replace the conventional anaerobic lagoon treating bagasse wash wastewater from agro-based pulp and paper mill, to generate bio-energy and to reduce greenhouse gas emissions. The plant was designed to treat 12 ML d⁻¹ of wastewater having two 5 ML capacity reactors, 5.75 kg COD m⁻³ d⁻¹ organic loading rate and 20 h hydraulic retention time. In the plant 80–85% COD reduction was achieved with biogas production factor of 520 L kg⁻¹ COD reduced. In 11 months 4.4 million m³ of biogas was generated from bagasse wash wastewater utilizing UASB process. Utilization of the biogas in the Lime Kiln saved 2.14 ML of furnace oil in 9 months. Besides significant economic benefits, furnace oil saving reduced 6.4 Gg CO₂ emission from fossil fuel and conversion of the anaerobic lagoon into anaerobic reactor reduced 2.1 Gg methane emission which is equal to 43.8 Gg of CO₂.     

Synthesis of olivine-type LiFePO4 by emulsion-drying method

Olivine-type, orthorhombic, LiFePO₄ powders with small particle size have been successfully synthesized by the emulsion-drying method. The electronic and crystal structure is analyzed by X-ray absorption spectroscopy (XAS) and X-ray diffraction Rietveld refinement. The powder calcined at 750 °C shows the highest discharge capacity of 125 mAh g⁻¹ with excellent cycle stability. The discharge capacity of this powder increases to 154 mAh g⁻¹ on increasing the addition of carbon black as a conductive agent up to 40 wt.%. In a rate capability test, the discharge capacity is completely recovered and retained up to the 700th cycle.     

Electrochemical characteristics of needle coke refined by molten caustic leaching as an anode material for a lithium-ion battery

Needle coke, the remaining material after refining petroleum, is used as an anode of a lithium-ion secondary battery. Sulfur is separated from the needle coke to below 0.1 wt.% using the molten caustic leaching (MCL) method developed at the Korea Institute of Energy Research. The needle coke with high-purity is carbonized at various temperatures, namely 0, 500, 700 and 900 °C. The coke treated at 700 °C gives a first and second discharge capacity of more than 560 and 460 mAh g⁻¹, respectively, between 0 and 2.0 V. By contrast, the first and second discharge capacity of untreated coke is over 420 and 340 mAh g⁻¹, respectively, between 0.05 and 2.0 V.The first discharge capacity of 560 mAh g⁻¹ is beyond the theoretical maximum capacity of 372 mAh g⁻¹ for LiC₆. Though the cycle efficiency is not consistent, the needle coke heat-treated at 700 °C persistently maintains an efficiency of over 90% until the 50th cycle, except on the first cycle. This study demonstrates that the needle coke with high-purity could be a good candidate for an anode material in fabricating high-capacity lithium-ion secondary batteries.     

LiMn2O4 cathode materials synthesized by the cellulose–citric acid method for lithium ion batteries

A new technique was employed to synthesize spinel LiMn₂O₄ cathode materials by adding cellulose and citric acid to an aqueous solution of lithium and manganese salts. Various synthesis conditions such as the calcination temperature and the citric acid-to-metal ion molar ratio (R) were investigated to determine the ideal conditions for preparing LiMn₂O₄ with the best electrochemical characteristics. The optimal synthesis conditions were found to be R = 1/3 and a calcination temperature of 800 °C. The initial discharge capacity of the material synthesized using the optimal conditions was 134 mAh g⁻¹, and the discharge capacity after 40 cycles was 125 mAh g⁻¹, at a current density of 0.15 mA cm⁻² between 3.0 and 4.35 V. Details of how the initial synthesis conditions affected the capacity and cycling performance of LiMn₂O₄ are discussed.     

Preparation of LiMn2O4 at the low temperature of 250 °C using eutectic self-mixing method

Spinel LiMn₂O₄ as a cathode material for lithium rechargeable batteries is prepared at the low temperature of 250 °C without any artificial mixing procedures of reactants. The phase transitions of lithium manganese oxide are found three times on heating at 250 °C. The prepared material exhibits the initial discharge capacity of 85.5 mAh g⁻¹ and the discharge capacity retention of 91.5% after 50 cycles.     

Sonochemical synthesis of amorphous manganese oxide coated on carbon and application to high power battery

The nanocomposite material of amorphous manganese oxide and acetylene black (HSMO/AB), was synthesized by sonochemical method. The acetylene black particles were homogeneously coated with amorphous manganese oxide. In order to demonstrate that these characteristic structures were suitable for rapid discharge–charge, the composite material was tested under large current density. The result exhibited 185 mAh g⁻¹ in specific discharge capacity under 10 A g⁻¹ in current density. Assuming that an operating voltage of 2.5 V, this capacity corresponded 20 kW kg⁻¹ in power density and 90 Wh kg⁻¹ in energy density.     

Comparative performances for primary lithium batteries of some covalent and semi-covalent graphite fluorides

Different graphite fluorides were prepared by three different synthesis ways: fluorination at room temperature, at 600 °C, and refluorination at 400 and 530 °C of a fluorinated graphite prepared at room temperature. All the samples have been characterized by ¹⁹F MAS NMR and FT-IR spectroscopies. Their electrochemical performances as cathode materials in primary lithium batteries have been investigated at room temperature and at 60 °C and as a function of the current density. Ageing behavior has been also studied using some liquid electrolytes. Refluorinated sample at 400 °C exhibits the best performances because of both its good average discharge potential and its discharge capacity, i.e. 2.54 V and 848 Ah kg⁻¹, respectively. For this sample, the best specific energy density and specific power density are 2149 Wh kg⁻¹ and 902 W kg⁻¹, respectively.     

Nucleate pool boiling of liquid methane and its natural gas mixtures

An apparatus was designed and built for the study on pool-boiling heat transfer characteristics of pure and mixed fluids at cryogenic temperature. With this apparatus, extensive measurements were carried out to investigate the pool-boiling behaviors of pure methane and three binary mixtures of methane + ethane, methane + propane and methane + isobutane, as well as a multicomponent mixture of methane, ethane, propane and isobutane. The present measurements were performed in a descending heat flux procedure ranging from 250 kW/m² to 30 kW/m² at a fixed pressure of 0.13 MPa. Comprehensive measured data were presented in this paper, and also compared with some existing correlations. The deviations between the measured data and the predicted results locate within ±25% range.     

Effect of chitosan on stabilization of acetates-containing solution: A novel precursor for LiMn2O4 film deposition

Due to the adequate viscosity of the chitosan-added precursor solutions, the films deposited from the chitosan-added precursor solution showed a higher deposition rate than the ones from the PVP-added solution under the same coating parameters. Furthermore, the chitosan-added precursor solution remained stable without any precipitation for at least 10 months. On the other hand, without the addition of chitosan, the precursor solution showed apparent precipitation after being stirred for 12 h. The enhanced stability of the precursor solution by the addition of chitosan is attributed to the complexation between metal ions and the –NH₂ groups of chitosan. And the electrochemical behavior for the deposited films calcined at 700 °C for 1 h was also characterized by charge–discharge test. The result revealed that the film deposited from chitosan-containing precursor solution possesses an initial discharge capacity of 134 mAh g⁻¹ and about 9% capacity loss after 50 charge/discharge cycles, which is better than the one deposited from chitosan-free precursor solution with an initial discharge capacity of 108 mAh g⁻¹ and 24% capacity loss after 50 cycles.     

High power-density single-chamber fuel cells operated on methane

Single-chamber solid oxide fuel cells (SC-SOFCs) incorporating thin-film Sm_0.15Ce_0.85O_1.925 (SDC) as the electrolyte, thick Ni + SDC as the (supporting) anode and SDC + BSCF (Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ) as the cathode were operated in a mixture of methane, oxygen and helium at furnace temperatures of 500–650 °C. Because of the exothermic nature of the oxidation reactions that occur at the anode, the cell temperature was as much as 150 °C greater than the furnace temperature. Overall, the open circuit voltage was only slightly sensitive to temperature and gas composition, varying from ∼0.70 to ∼0.78 V over the range of conditions explored. In contrast, the power density strongly increased with temperature and broadly peaked at a methane to oxygen ratio of ∼1:1. At a furnace temperature of 650 °C (cell temperature ∼790 °C), a peak power density of 760 mW cm⁻² was attained using a mixed gas with methane, oxygen and helium flow rates of 87, 80 and 320 mL min⁻¹ [STP], respectively. This level of power output is the highest reported in the literature for single chamber fuel cells and reflects the exceptionally high activity of the BSCF cathode for oxygen electro-reduction and its low activity for methane oxidation.     

Hydrogen storage in an activated carbon bed: Effect of energy release on storage capacity of the tank

Thermal effects during dynamic charging of a two-liter, adsorbent, packed bed, hydrogen storage tank were studied through numerical modeling. For packed-bed materials having adsorption capacities smaller than 2 wt%, the conversion to heat of the mechanical work required to feed the tank produces more than 60% of the temperature increase that occurs during the charging process. However, for materials having adsorption capacities greater than 3 wt%, 60% of the heating is due to the adsorption process. The temperature increase for a material that would fulfill the DOE recommendation of 6 wt% storage capacity is 130 K. This reduces the storage capacity by 20% relative to what would be obtained from an isothermal charging process. Simulations showed that the limitation in the storage capacity can be reduced to less than 10%, if a packed bed having an effective conductivity of a few W m^?1 K^?1 can be used.     

Electrochemical properties of the Li-ion polymer batteries with P(VdF-co-HFP)-based gel polymer electrolyte

Gel polymer electrolytes consisting of 25 wt.% P(VdF-co-HFP), 65 wt.% ethylene carbonate + propylene carbonate and 10 wt.% LiN(CF₃SO₂)₂ are prepared using by a solvent-casting technique. The electrodes are for use in lithium-ion polymer batteries. The electrochemical characteristics of the gel polymer electrolytes are evaluated by means of ac impedance and cyclic voltammetry. The charge–discharge performance of lithium polymer and lithium-ion polymer batteries is examined. A LiCoO₂ | gel polymer electrolyte (GPE) | mesocarbon microbeads (MCMB) cell delivers a discharge capacity of 146.8 and 144.5 mAh g⁻¹ on the first and the 20th cycle, respectively. The specific discharge capacity is greater than 140 mAh g⁻¹ for up to 20 cycle at all the current densities examined.     

The impact of increasing organic loading in two phase digestion of food waste

This paper examines the impact of increasing organic loading in a two phase anaerobic digestion system treating commercial food waste. The first phase is a series of sequentially fed leach bed reactors (LBRs). The second phase is an upflow anaerobic sludge bed (UASB). Leachate from the leach beds, form the influent to the UASB. Effluent from the UASB is re-circulated over the leach beds. Flow rates corresponded to 1 volume of leachate per effective LBR volume per day. The theoretical organic loading rate (OLR) of the UASB is based on the conversion of volatile solids (VS) in the LBR to chemical oxygen demand (COD). The experiment was set up such that the theoretical OLR would rise from 7.1 to 8.8 to 11.8 kg COD m⁻³ day⁻¹.The system operated effectively at the lowest organic loading rate producing 384 L CH₄ kg VS⁻¹ which corresponded to 72% of the value obtained in a BMP test. COD conversion efficiency was recorded at 75%. The accumulation of COD over the life of the experiment led to a situation whereby the volumetric OLR (product of COD concentration in the leachate by the flow rate) was over twice the theoretical OLR at the end of the experiment (24.3 kg VS m⁻³ day⁻¹ versus 11.8 kg VS m⁻³ day⁻¹). At the highest loading rate total ammonia nitrogen (TAN) reached levels of 4500 mg L⁻¹ with pH levels of 8.15. This resulted in significant reduction of methane production.     

A thin film silicon anode for Li-ion batteries having a very large specific capacity and long cycle life

A thin film of Si was vacuum-deposited onto a 30 μm thick Ni foil from a source of n-type of Si, the film thickness examined being 200–1500 Å. Li insertion/extraction evaluation was performed mainly with cyclic voltammetry (CV) and constant current charge/discharge cycling in propylene carbonate (PC) containing 1 M LiClO₄ at ambient temperature. The cycleability and the Li accommodation capacity were found to depend on the film thickness. Thinner films gave larger accommodation capacity. A 500 Å thick Si film gave a charge capacity over 3500 mAh g⁻¹ being maintained during 200 cycles under 2 C charge/discharge rate, while a 1500 Å film revealed around 2200 mAh g⁻¹ during 200 cycles under 1 C rate. The initial charge loss could not be ignored but it could be reduced by controlling the deposition conditions.     

Properties of containing Sn nanoparticles activated carbon fiber for a negative electrode in lithium batteries

Activated carbon fiber (ACF) containing Sn nanoparticles were prepared by impregnation and were investigated as a negative electrode material in lithium batteries. The tin particle size was controlled by selecting an ACF with an adequate surface structure. This Sn/ACF composite cycled versus Li metal showed a first discharge capacity as high as 200 mAh g⁻¹ compared to the pristine ACF which showed only 87 mAh g⁻¹. Excellent cyclability with these composites was obtained with ACF BET SSA as large as 2000 m² g⁻¹ and 30 wt.% Sn.