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1.
Liquefaction, cracking and hydrogenation of microalgae biomass resources to ▫$CO_2$▫ negative advanced biofuels : mechanisms, reaction microkinetics and modelling
Dana Marinič, Miha Grilc, Brigita Hočevar, Florian Delrue, Blaž Likozar, 2023, izvirni znanstveni članek

Opis: Deoxygenation of triglycerides is one of the crucial pathways for the production of oxygen-free hydrocarbons and biofuels that are fully compatible with conventional internal combustion engines. The one-step liquefaction and hydrotreatment of Chlorella sorokiniana microalgae was investigated in a three-phase slurry reactor. The production of diesel-like hydrocarbons was successfully accomplished over sulfide form of NiMo/Al2O3 catalyst under hydrogen atmosphere. The present work contains a comprehensive investigation of the temperature and hydrogen pressure influence on the final product composition. The highest yield of C18 and C16 (26.1% and 10.7%, respectively) was reached by increasing the reaction temperature to 350 °C and hydrogen pressure to 50 bar, while at milder conditions (200 °C and 20 bar) the products appeared only in trace concentrations. In order to obtain an accurate kinetic model, reaction mechanism was first needed to be determined based on experimentally obtained products and intermediates. A simplified reaction pathway contains liquefaction, hydrogenolysis, hydrodeoxygenation, decarboxylation and decarbonylation. The model comprises mass transfer phenomena involved in the liquefaction process, the mass transfer of hydrogen from gas to liquid phase, adsorption, desorption and surface reaction kinetics. The lowest rate constant was calculated for the microalgae conversion to triglycerides (k0 = 1.93 × 10−6 min−1), indicating slow liquefaction.
Ključne besede: Microalgae, Biofuel, Liquefaction, Hydrodeoxygenation, One-pot reaction
Objavljeno v DKUM: 17.07.2023; Ogledov: 329; Prenosov: 18
.pdf Celotno besedilo (5,61 MB)
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2.
Post-liquefaction volume change in micaceous sandy of Old Gediz River Delta
Ender Basari, Gurkan Ozden, 2013, izvirni znanstveni članek

Opis: Post-liquefaction settlement characteristics of micaceous sands are not well investigated topic. Currently available charts relating post-liquefaction volumetric strain to relative density were developed for clean sand. Estimation of post-liquefaction settlement of micaceous sands, therefore, may stay on the unsafe side, since there is evidence indicating that mica grains could increase volume change tendency. Influence of mica content on post-liquefaction volumetric strain of sand-mica mixtures is studied in this article. Soil samples were prepared at various relative densities. Influence of fine content that could be present in the field was also investigated on tamped natural field samples recovered from boreholes drilled in a highly populated alluvial site known as the Old Gediz River Delta of Izmir. It was found that increasing mica content at a certain relative density resulted in higher volumetric strains as compared with the data on clean sands. It is deduced that influence of mica grains on sand behavior depends on initial void ratio of sand. Effects of mica grains decrease with increasing of relative density. Simple empirical relationships were derived relating mica content and relative density to volumetric strain. It was also noticed that fine content accelerated and increased post-liquefaction volumetric strains.
Ključne besede: sand, mica, non-plastic fines, post-liquefaction volume change
Objavljeno v DKUM: 14.06.2018; Ogledov: 859; Prenosov: 88
.pdf Celotno besedilo (434,60 KB)
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3.
Soil liquefaction in the Tone river basin during the 2011 earthquake off the Pacific coast of Tohoku
Stanislav Lenart, Junichi Koseki, Yukika Miyashita, 2012, izvirni znanstveni članek

Opis: A brief report about the liquefaction damage in the Tone river basin, caused by the 2011 earthquake off the Pacific coast of Tohoku, is presented. It includes sand boiling, damage to river dikes, the settlement and tilt of superstructures, the uplift of light underground structures and lateral spreading. A history of land reclamation along the Tone river is briefly presented to understand why extensive liquefaction took place predominantly inreclaimed land. The recorded ground motions near the river were analyzed andcompared to near-source ground motions. The effects of the site location and the ground conditions during the peak ground acceleration are discussed.
Ključne besede: 2011 earthquake off the Pacific coast of Tohoku, liquefaction, case history
Objavljeno v DKUM: 13.06.2018; Ogledov: 1180; Prenosov: 172
.pdf Celotno besedilo (1,65 MB)
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4.
Effect of the initial structure on the behaviour of Chlef sand
Noureddine Della, Ahmed Arab, Mostefa Belkhatir, Hanifi Missoum, Claude Bacconnet, Daniel Boissier, 2010, izvirni znanstveni članek

Opis: It has been known for many years that initial structure, plays an important part in the results of laboratory testing of natural of silty sands. For this purpose, a series of monotonic undrained triaxial compression tests were carried out on samples composed of Chlef sand with 0.5% non-plastic silt content using two depositional methods (dry funnel pluviation and wet deposition) at different initial relative density (RD= 29%, 50% and 80%). All specimens were subjected to isotropic consolidation of 50 kPa, 100 kPa and 200 kPa. It was found that the initial structure of the soil influences considerably the undrained shear response in terms of maximal deviatoric stress, peak strength and excess pore water pressure.
Ključne besede: liquefaction, sand, dry funnel pluviation, wet deposition, density, deviatoric stress, pore pressure
Objavljeno v DKUM: 11.06.2018; Ogledov: 896; Prenosov: 77
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5.
The response of saturated soils to a dynamic load
Stanislav Lenart, 2008, izvirni znanstveni članek

Opis: This paper presents the two most significant types of deformation behavior fordynamically loaded, saturated soil. Flow liquefaction and cyclic mobility deserve special attention because of the large deformations that accompany these two phenomena. The submergence of a railway-line embankment due to the newly built Sava-river accumulation reservoir in Boštanj and the large landslide that occurred in the Stože area in the Julian Alps are case histories in Slovenia where flow liquefaction and cyclic mobility were analyzed. The dynamic loading caused by railway traffic and possible seismic activity were taken into account. Material from these two sites, silty sand and lacustrine carbonate silt, were used in extensive laboratory research, with the objective to define a procedure for excess pore-water pressure-generation modeling in dynamically loaded saturated soil. It has been found recently that the change of the pore-water pressure is related to the dissipated energy density calculated from the hysteresis loops caused by dynamic loading. Based on the experimental results an empirical equation defining the generation of pore pressure during dynamic loading has been proposed. The equation is divided into two parts: the first part describing the residual pore-water pressure generation, and the second part describing the increment and decrement of pore-water pressure within the load cycle, the so-called temporary pore-water pressure change. The proper effective stresses and thus the stress path of the dynamically loaded soil can be defined by using the proposed energy-based numerical model. The proposed pore-pressure model can also be used in deformation-behavior modeling. It was observed from the experimental results that after a few cycles of dynamic loading the saturated soil starts to exhibit a very low stiffness at the beginning of a load cycle, after which it begins to strengthen. The strain developed during this softening phase represents the main share of the total strain. The occurrence and duration of this phase are related to the energy dissipated during the cyclic loading as well, and the relation between the dissipated energy, the excess pore pressure and the short-term flow during cyclic mobility, give us an opportunity for a simple response modeling of the dynamically loaded saturated soils.
Ključne besede: flow liquefaction, cyclic mobility, excess pore pressure, dissipated energy
Objavljeno v DKUM: 05.06.2018; Ogledov: 1053; Prenosov: 222
.pdf Celotno besedilo (370,70 KB)
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6.
Cyclic liquefaction potential of lacustrine carbonate from Julian Alps
Bojan Žlender, Stanislav Lenart, izvirni znanstveni članek

Opis: This paper presents the liquefaction studies of lacustrine carbonate silt from the Julian Alp landslide Stože. Geological conditions of the region and geomechanical characteristics of the ground were investigated. The research project was performed with the intention to determine the effects of cyclic loading on lacustrine carbonate silt. Investigation with 77 cyclic triaxial tests was performed on universal triaxial apparatus Wykeham Farrance UP 100 TR, in the Laboratory of soil mechanics, Faculty of Civil Engineering, University of Maribor. The essential equipment comprises cylindrical triaxial apparatus with a cell, a press with appurtenant electro-mechanic equipment, measuring equipment, and computer hardware and software equipment. Specimens with dimensions of height = 140 mm and diameter = 70 mm were saturated, then subjected to the arbitrary initial isotropic stress state and consolidated with vertical and radial draining, and then loaded with distortional loading of chosen dynamical axial force (frequency f = 1 Hz). A set of tests with a spectrum of different stress states and cyclic loading were performed. This research showed that lacustrine carbonate silt is a highly sensitive material.The resistance to liquefaction was somewhat higher than that of typical clean sand, but a perceivable excess pore pressure generation, which causes the decrease of strength parameters, was noticed. Test results of cyclic triaxial tests indicate dynamic characteristics of lacustrine carbonate silt and wide applicability of the test method.
Ključne besede: civil engineering, geomechanics, soil investigations, lacustrine carbonate silt, cyclic triaxial tests, liquefaction potential, shear modulus, damping ratio, cyclic stress ratio, pore pressure ratio
Objavljeno v DKUM: 15.05.2018; Ogledov: 1610; Prenosov: 135
.pdf Celotno besedilo (1,53 MB)
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