Although biodiesel has a promising potential to be used as an alternative fuel for compression-ignition engines, its use may deteriorate engine performance. The objective of the current study was to ...enhance the performance of a compression-ignition engine operated with a diesel-biodiesel blend using diethyl ether (DEE). Four fuels were examined in a diesel engine to assess its performance and analyze the combustion process. These fuels were diesel, biodiesel-diesel mixture, and two mixtures of biodiesel-diesel-DEE with DEE proportions of 5% and 10% by volume. It was found that using diesel-biodiesel blend increased the minimum brake specific fuel consumption (bsfc) and reduced the maximum thermal efficiency by 8.1% and 6.8%, respectively, compared to diesel fuel. However, employing 5% DEE in the diesel-biodiesel mixture improved engine performance considerably for most engine loads in comparison with all fuels. Altering the fuel type had no significant impact on combustion start instant. However, the heat release rate was lower and combustion duration was longer for diesel compared to other fuels at higher engine loads. Using DEE did not significantly affect engine stability.
Display omitted
•High quality GO membranes can be coated on polymer substrate by spray coating method.•Prepared GO membranes offer gas characteristics similar to those made by filtration.•Dilute GO ...suspension in spray coating reduces the formation of extrinsic wrinkles.•Less wrinkles results in reduction in the porosity of inter-layer galleries.•Less wrinkles leads to higher selectivity of H2 over large gas molecules.
Graphene oxide (GO) membranes have shown promising gas separation characteristics specially for hydrogen showing potential for industrial applications. However, GO membranes made by filtration, the most common synthesis method, contain wrinkles affecting their gas separation characteristics and the method itself is difficult to scale up. In this work, high quality GO membranes are made from GO suspension by easily scalable spray coating technique (and also by filtration method for comparison) on hydrophilic polyester track etch substrates. GO sheet suspensions of large sheet average size (33 µm) and dilute concentrations are used to minimize GO sheet edge-to-edge interactions and minimize extrinsic wrinkle formation. Single gas permeation and separation experiments of equimolar H2/CO2 binary mixture were conducted to evaluate the permeation and separation characteristics of prepared membranes. GO membranes prepared by spray coating offer gas characteristics similar to those made by filtration, however using dilute GO suspension in spray coating reduces the formation of extrinsic wrinkles causing reduction in the porosity of the inter-sheet pathway where the transport of large gas molecules dominates. This study demonstrates an efficient, scalable and cost-effective approach for synthesizing large area GO membranes with enhanced hydrogen separation.
Methane which can be produced from biogas has a great potential to be used as an alternative renewable fuel for spark-ignition engines. However, engines need to be optimized for methane use. The aim ...of this study was to numerically optimize a spark-ignition engine fueled with methane and operated at a constant speed of 1,500 rpm via using a validated two-zone combustion model. The model was able to predict engine performance parameters, NO emission, and engine knock at different engine operating conditions including inlet pressure, compression ratio, and excess air factor. Engine knock was prevented by increasing the excess air factor up to 1.2 when the engine operated with higher inlet pressure and compression ratio. It was found that a maximum inlet pressure of only 120 kPa could be used with an engine compression ratio of 14 and excess air factor of 1.2 for knock free operation. The peak engine power was produced when the engine operated with an inlet pressure of 200 kPa and compression ratio of 8 or 9. It was also found that the optimum operating condition which resulted in high engine power accompanied with low fuel consumption and high efficiency was obtained when the engine operated with an inlet pressure of 180 kPa and a compression ratio of 11. This condition required the engine to operate with an excess air factor of 1.19 to prevent engine knock. However, operating the engine at this optimum condition would be accompanied with high NO emission.
Graphene oxide (GO) membranes offer attractive gas separation properties. However, the gas separation mechanism for GO membranes is unclear due to inconsistent permeation and separation results ...reported in the literature. In this work, pure gas permeation and separation of equimolar (H2/CO2) mixture experiments were conducted on GO membranes made from large GO sheets of different sizes (33 and 17µm) to understand the gas permeation and separation characteristics of these membranes. At room temperature the permeation of large molecules (CH4, N2 and CO2,) through GO membranes exhibits Knudsen–like diffusion characteristics, with the permeance for the small sheet GO membrane about twice that for the large sheet GO membrane. The smaller gases (H2 and He) exhibit much higher permeance, showing additional transport in additional pathway. The GO membranes show good H2/CO2 selectivity for both pure and binary gas feeds, without CO2 pore blockage effect for mixture separation found for crystalline microporous membranes. An inter-sheet and inner-sheet two-pathway model is proposed which can explain the results obtained in this work. Gas permeation in GO membranes, more complex than in crystalline microporous membranes, is determined by solubility (surface properties), diffusivity (relative molecular size to pore size), porosity and tortuosity of both the inter-sheet pores and inner-sheet defect pores. These properties are strongly influenced by synthesis method and conditions for GO sheets and membranes.
Display omitted
•Gas separation on large-sheet GO membranes was performed to elucidate gas transport mechanism of GO membranes.•GO membranes are hydrogen selective in both pure and mixture gas feeds.•The permeation/separation results can be explained semi-quantitatively by a two-pathway model.
Display omitted
•Intermittent curing at 70°C applied on 4 steps 6h each followed by 18h at room temperature.•Intermittent curing improved the UCS at the end of each curing step.•The effect of resting ...period and added water content on UCS was investigated.•Increasing the AL-to-FA content is sensitive to the Na2O-to-SiO2 mole ratio.•Very low H2O-to-Na2O and high Na2O-to-SiO2 mole ratios have inverse effect on UCS.
The research work focuses on the production of type F fly ash based geopolymer using intermittent curing. Two different types of soluble sodium silicate and Na(OH) solution with three different mole ratios were used with a fixed ratio. Two different fly ash-to-alkaline liquid activator ratios were used with and without additional water content. Two different resting periods were checked prior to starting the curing regime. The curing temperature was set at 70°C applied intermittently on 4 steps for 6h each per day followed by 18h rest at ambient temperature. Twenty-one different geopolymer mixtures were cast using a mixture of fly ash and natural sand at a fixed ratio. The gain of compressive strength was checked at age 24, 48, 72, and 96h and 7days. Intermittent curing proved to increase the compressive strength of all geopolymer mortar at the end of each curing step. Thirteen geopolymer mixtures exceeded the Egyptian Code of Practice limit set for the 7-day compressive strength at 27MPa. The UCS is directly proportional to the increase of the specific gravity of the soluble sodium silicate used, the age, the Na(OH) solution mole concentration, the alkaline liquid activator-to-fly ash ratio, the resting period and the Na2O-to-SiO2 mole ratio. Yet, it is inversely proportional to additional water content, H2O-to-Na2O mole ratio and the water-to-geopolymer solids ratio.
•HTL was conducted on Galdieria sulphuraria microalgae for 30 min at 300 °C and 9 MPa.•HTL biochar pyrolysis was investigated using TGA experiments and fixed bed reactor configuration.•Pyrolysis ...experiments were carried out in a batch membrane reactor equipped with Pd77Ag23 hydrogen-selective membrane.•Two thirds of the produced hydrogen is recovered in the permeate stream of Pd77Ag23 membrane.•The retentate stream shows reduced CO and CO2 as well as increased CH4 content.
Algal biomass has recently emerged as a sustainable feedstock that can be converted to liquid fuels and other energy products. Hydrothermal liquefaction (HTL) is considered one of the most efficient thermochemical conversion techniques to produce high-quality biocrude oil that can be upgraded into a variety of liquid fuels. However, failure to identify practical uses for the HTL residual solids (biochar) could make the process economically less attractive especially with low lipid algae. This work investigates the conversion of HTL biochar of microalgae Galdieria sulphuraria to hydrogen under pyrolysis conditions in a membrane reactor capable of selectively separating hydrogen from the reaction zone. HTL biochar pyrolysis was first investigated using thermogravimetric analysis experiments and fixed bed reactor configuration. Batch membrane reactor pyrolysis experiments were then carried out using Pd77Ag23 hydrogen-selective membrane. The involvement of a Pd77Ag23 membrane in the reactor during the pyrolysis of biochar results in the recovery of hydrogen in the permeate stream (~2 times the hydrogen remaining in the retentate) and further facilitates the conversion of biochar to gaseous fuels. The retentate stream shows reduced CO and CO2 as well as increased CH4 content compared to pyrolysis conditions with no membrane.
Highly b‐oriented, closely packed, MFI zeolite films are prepared on seeded stainless‐steel plates using organic template‐free, secondary growth solutions, containing aluminum sulfate as a ...crystallization agent. The number of a‐oriented twin crystals is significantly reduced, and even eliminated, simply by restricting the pH value of the secondary growth solution to the narrow range of 11.1–11.3. Values of pH can be adjusted through the controlled addition of (NH4)2SO4 or H2SO4 to secondary growth solutions of the composition (1 SiO2:0.57 NaOH:137.5 H2O:0.0050 (Al2(SO4)3⋅18 H2O)) or by simply decreasing the molar composition of NaOH with no extra additives.
Thin films: The effect of compositional constraints on the synthesis of highly b‐oriented MFI zeolite films on stainless‐steel plates using secondary growth solutions, free of organic template, was investigated. The number of twin crystals can be significantly reduced, and even eliminated, simply by restricting the pH value of the secondary growth solutions to the narrow range of 11.1–11.3.
A simulation study to predict and optimize a natural gas steam reforming plant in Suez was performed. The developed model was used to generate performance data that would map the relation between ...atthe operating variables and hydrogen productivity. A single objective optimization problem was then formulated to maximize hydrogen production in the subunits: hydrocarbon prereformer, steam methane reformer, and the medium‐temperature water‐gas‐shift reactor. The process temperature and pressure for the three subunits, total plant flow rate and total superheated steam flow rate were selected as decision variables. A good agreement was found between simulation results and plant data at steady‐state conditions in terms of hydrogen yield and chemical composition. The developed mathematical model for hydrogen productivity correctly predicts the effect of relevant process parameters.
A simulation study is presented for a natural gas steam reforming plant. Simulation results were validated against plant data under steady‐state conditions. A simulation tool was developed to identify the optimal operating conditions and predict the plant hydrogen productivity. Optimized conditions for the complete industrial hydrogen plant maximize the added value and minimize the running cost.
We studied BCR-ABL1 transcript levels in patients with chronic myeloid leukemia in chronic phase (CML-CP) at 3, 6, and 12 months after starting imatinib to identify molecular milestones that would ...predict for overall survival (OS) and other outcomes more reliably than serial marrow cytogenetics.
We analyzed 282 patients with CML-CP who received imatinib 400 mg/d as first-line therapy followed by dasatinib or nilotinib if treatment with imatinib failed. We used a receiver operating characteristic curve to identify the cutoffs in transcript levels at 3, 6, and 12 months that would best predict patient outcome. We validated our findings in an independent cohort of 95 patients treated elsewhere.
Patients with transcript levels of more than 9.84% (n = 68) at 3 months had significantly lower 8-year probabilities of OS (56.9% v 93.3%; P < .001), progression-free survival, cumulative incidence of complete cytogenetic response, and complete molecular response than those with higher transcript levels. Similarly, transcript levels of more than 1.67% (n = 87) at 6 months and more than 0.53% (n = 93) at 12 months identified high-risk patients. However, transcript levels at 3 months were the most strongly predictive for the various outcomes. When we compared OS for the groups defined molecularly at 6 and 12 months with the usual cytogenetic milestones, categorization by transcript numbers was the only independent predictor for OS (relative risk, 0.207; P < .001 and relative risk, 0.158; P < .001, respectively).
A single measurement of BCR-ABL1 transcripts performed at 3 months is the best way to identify patients destined to fare poorly, thereby allowing early clinical intervention.
Shale reservoirs are characterized by very low permeability in the scale of nano-Darcy. This is due to the nanometer scale of pores and throats in shale reservoirs, which causes a difference in flow ...behavior from conventional reservoirs. Slip flow is considered to be one of the main flow regimes affecting the flow behavior in shale gas reservoirs and has been widely studied in the literature. However, the important mechanism of gas desorption or adsorption that happens in shale reservoirs has not been investigated thoroughly in the literature. This paper aims to study slip flow together with gas desorption in shale gas reservoirs using pore network modeling. To do so, the compressible Stokes equation with proper boundary conditions was applied to model gas flow in a pore network that properly represents the pore size distribution of typical shale reservoirs. A pore network model was created using the digitized image of a thin section of a Berea sandstone and scaled down to represent the pore size range of shale reservoirs. Based on the size of pores in the network and the pore pressure applied, the Knudsen number which controls the flow regimes was within the slip flow regime range. Compressible Stokes equation with proper boundary conditions at the pore’s walls was applied to model the gas flow. The desorption mechanism was also included through a boundary condition by deriving a velocity term using Langmuir-type isotherm. It was observed that when the slip flow was activated together with desorption in the model, their contributions were not summative. That, is the slippage effect limited the desorption mechanism through a reduction of pressure drop. Eagle Ford and Barnett shale samples were investigated in this study when the measured adsorption isotherm data from the literature were used. Barnett sample showed larger contribution of gas desorption toward gas recovery as compared to Eagle Ford sample. This paper has produced a pore network model to further understand the gas desorption and the slip flow effects in recovery of shale gas reservoirs.
PDF
