Habib Belayouni

Pyrolysis of waste animal fats in a fixed-bed reactor: Production and characterization of bio-oil and bio-char

Several animal (lamb, poultry and swine) fatty wastes were pyrolyzed under nitrogen, in a laboratory scale fixed-bed reactor and the main products (liquid bio-oil, solid bio-char and syngas) were obtained. The purpose of this study is to produce and characterize bio-oil and bio-char obtained from pyrolysis of animal fatty wastes. The maximum production of bio-oil was achieved at a pyrolysis temperature of 500 °C and a heating rate of 5 °C/min. The chemical (GC-MS analyses) and spectroscopic analyses (FTIR analyses) of bio-oil showed that it is a complex mixture consisting of different classes of organic compounds, i.e., hydrocarbons (alkanes, alkenes, cyclic compounds...etc.), carboxylic acids, aldehydes, ketones, esters,...etc. According to fuel properties, produced bio-oils showed good properties, suitable for its use as an engine fuel or as a potential source for synthetic fuels and chemical feedstock. Obtained bio-chars had low carbon content and high ash content which make them unattractive for as renewable source energy.

Paleogeographic and geodynamic Miocene evolution of the Tunisian Tell (Numidian and Post-Numidian Successions): bearing with the Maghrebian Chain

The Numidian and Post-Numidian stratigraphy of the Tunisian Tell has been updated based on 16 stratigraphic sections belonging to the Massylian sub-domain of the Maghrebian Flysch Basin and to the External Domain. The new data concern detailed litho- and biostratigraphy, gaps, synchronous marker levels, lateral correlations, tectonic contacts, etc. The successions studied show many diachronous and unconformity boundaries delimiting sedimentary depositional sequences related to some tectonic/sedimentary processes. Two main Miocene sedimentary successions (Numidian and Post-Numidian) are recognized overlying the Sub-Numidian Succession (pre-Early Aquitanian) by new integrated (planktonic foraminifera and calcareous nannoplankton) chronostratigraphic analyses, allowing an update of the formations studied. The Miocene tectonic/sedimentary relationships and the timing of the deformation are summarized as follows: (1) the activation of a foredeep stage and a tectogenesis phase gives rise to an accretionary orogenic wedge during mainly the Early Miocene; (2) a late-orogenic phase is checked in the Late Burdigalian-Early Langhian characterized by a marine glauconitic terrigenous sedimentation; (3) a post-orogenic generalized phase is confirmed from the Middle Miocene on in shallow marine or continental sedimentation. These results show good correlation along the Maghrebian Chain and Betic Cordillera. Finally, a paleogeographic and geodynamic evolutionary model concerning the Miocene African Tunisian Margin is postulated.

A study of the organic matter in Tunisian phosphates series: Relevance to phosphorite genesis in the Gafsa Basin (Tunisia)

Abstract In the Gafsa Basin, Tunisia, peloidal fracolite is interbedded with shales, limestones and rocks of intermediate lithology. The rocks were deposited in an epicontinental sea and have been buried no more than 500 m. The organic matter they contain is, therefore, thermally immature and, in all units, derived mainly from marine plankton, particularly Dinoflagellates. The organic matter in the phosphorite units is composed predominantly of humic acids (HA) which are essentially located within the pellets. These pellets are surrounded by an outer matrix in which the organic matter is similar to the kerogen comprised in the shally strata alternating with the phosphorite and limestone beds. During weathering, the content of the organic matter assocciated with the matrix decreases more rapidly than that of the organic matter entrapped within the pellets. Geochemical and palynological study of the organic matter in interbedded rocks of different lithology (shale, limestone, phosphorite) suggest that the shales were deposited in a reducing environment, the limestones in one that was oxic, whilst the phosphorites were formed in a redox environment inermediate between the two. The interpretation of the data presented in this paper is that the genesis of shales, phosphate and some carbonate beds (excluding coquinas) did not result from the deposition of initially sharply differentiated sediments but resulted from differences in diagenesis of sediments initially containing planktonic organic matter associated with clay and carbonate minerals.

New data on the Vrancea Nappe (Moldavidian Basin, Outer Carpathian Domain, Romania): paleogeographic and geodynamic reconstructions

A study has been performed on the Cretaceous to Early Miocene succession of the Vrancea Nappe (Outer Carpathians, Romania), based on field reconstruction of the stratigraphic record, mineralogical-petrographic and geochemical analyses. Extra-basinal clastic supply and intra-basinal autochthonous deposits have been differentiated, appearing laterally inter-fingered and/or interbedded. The main clastic petrofacies consist of calcarenites, sub-litharenites, quartzarenites, sub-arkoses, and polygenic conglomerates derived from extra-basinal margins. An alternate internal and external provenance of the different supplies is the result of the paleogeographic re-organization of the basin/margins system due to tectonic activation and exhumation of rising areas. The intra-basinal deposits consist of black shales and siliceous sediments (silexites and cherty beds), evidencing major environmental changes in the Moldavidian Basin. Organic-matter-rich black shales were deposited during anoxic episodes related to sediment starvation and high nutrient influx due to paleogeographic isolation of the basin caused by plate drifting. The black shales display relatively high contents in sub-mature to mature, Type II lipidic organic matter (good oil and gas-prone source rocks) constituting a potentially active petroleum system. The intra-basinal siliceous sediments are related to oxic pelagic or hemipelagic environments under tectonic quiescence conditions although its increase in the Oligocene part of the succession can be correlated with volcanic supplies. The integration of all the data in the “progressive reorientation of convergence direction” Carpathian model, and their consideration in the framework of a foreland basin, led to propose some constrains on the paleogeographic-geodynamic evolutionary model of the Moldavidian Basin from the Late Cretaceous to the Burdigalian.

Geostatistical optimization of water reservoir characterization case of the “Jeffra de Medenine” aquifer system (SE Tunisia)

AbstractThis study attempts to characterize the organization, geometry and continuity of aquifer systems in a faulted setting, by geostatistical methods. It concerns the “Jeffara de Medenine” aquifers, in South-Eastern Tunisia. The quality of architectural reservoir modelling depends heavily on available data and on the fault network at the origin of its compartmentalization. In our case study, the available data consist mainly of boreholes: (i) usually sparse: the data distribution and density are very uneven within the study area, depending on the aquifers and the river network; (ii) they do not, usually penetrate the entire aquifer formation. Therefore, aquifers situated at a great depth remain unattainable for many drillings, leaving large areas under-informed and (iii) they are supplemented by seismic data which, although of variable quality, provide useful information for building the fault network at a large scale. To deal with this lack of data, an original geostatistical approach is applied in or...

Variogram Identification Aided by a Structural Framework for Improved Geometric Modeling of Faulted Reservoirs: Jeffara Basin, Southeastern Tunisia

This article describes a proposed work-sequence to generate accurate reservoir-architecture models, describing the geometry of bounding surfaces (i.e., fault locations and extents), of a structurally complex geologic setting in the Jeffara Basin (South East Tunisia) by means of geostatistical modeling. This uses the variogram as the main tool to measure the spatial variability of the studied geologic medium before making any estimation or simulation. However, it is not always easy to fit complex experimental variograms to theoretical models. Thus, our primary purpose was to establish a relationship between the geology and the components of the variograms to fit a mathematically consistent and geologically interpretable variogram model for improved predictions of surface geometries. We used a three-step approach based on available well data and seismic information. First, we determined the structural framework: a seismo-tectonic data analysis was carried out, and we showed that the study area is cut mainly by NW–SE-trending normal faults, which were classified according to geometric criteria (strike, throw magnitude, dip, and dip direction). We showed that these normal faults are at the origin of a large-scale trend structure (surfaces tilted toward the north-east). At a smaller scale, the normal faults create a distinct compartmentalization of the reservoirs. Then, a model of the reservoir system architecture was built by geostatistical methods. An efficient methodology was developed, to estimate the bounding faulted surfaces of the reservoir units. Emphasis was placed on (i) elaborating a methodology for variogram interpretation and modeling, whereby the importance of each variogram component is assessed in terms of probably geologic factor controlling the behavior of each structure; (ii) integrating the relevant fault characteristics, which were deduced from the previous fault classification analysis, as constraints in the kriging estimation of bounding surfaces to best reflect the geologic structure of the study area. Finally, the estimated bounding surfaces together with seismic data and variogram interpretations were used to obtain further insights into the tectonic evolution of the study area that has induced the current reservoirs configuration.

A Constrained Geostatistical Approach for Efficient Multilevel Aquifer System Characterization

In this study, the problems of parameter estimation for systems with scarce measurements are examined. In this case, an original geostatistical methodology is applied to generate bathymetric surface models of a faulted aquifer system within the Jeffara Basin in southeastern Tunisia. The modelling workflow is based on i) the spatial analysis of the data configuration and ii) the conceptual stacking pattern. This allows provision of key concepts and geostatistical approaches to be undertaken during geomodelling procedures. In fact, two constraints have been integrated: i) inequality data provided by the end of the boreholes and ii) the faults that compartmentalize the aquifer system. First, kriging with inequality was used for depth estimation of the Turonian reservoir Top. The results are compared with those from classical kriging and evaluated through the estimation quality, the adopted assumptions and the method limitations. Validation analyses show that the model developed with the inequality data leads to a significant gain in mapping accuracy and geological realism. In the second step, the geostatistical approach was used to model the successive bounding surfaces of the aquifer system units. Consequently, the kriging constrained by inequality data could be applied in a variety of hydrogeological parameters interpolations to provide significantly better informative maps that are useful for hydrodynamic modelling. KeywordsGeostatistics; Surface Interpolation; Exact Data; Inequality Data; Geological Constraints

Characterization of syngas and bio-char: Co-products from pyrolysis of waste fish fats

Waste fish fats from Tunisian fish industry were pyrolyzed under nitrogen in a laboratory scale fixed-bed reactor. The pyrolysis was performed with a heating rate of 5°C/min from the ambient up to a final temperature of 500°C. In these conditions the main product is bio-oil (55 wt.%) while the co-products are syngas (44 wt.%) and bio-char (1 wt.%). The objective of this work is to characterize syngas and bio-char, to improve this technology in environmental and economic terms. The bio-char is characterized using elemental analysis (CHNS), moisture content, Fourier Transform Infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses furthermore the syngas composition is determined during the pyrolysis reaction. From the obtained results, we can conclude that the characterization of the pyrolysis by-products indicate that: (i) The syngas contains CH, CO2, CO and H2S; (ii) The bio-char characterization by elemental analyses indicates a high oxygen content and a moderate carbon content; these properties are confirmed by a high proportion of oxygenated functions and a modest aliphaticity (FTIR analyses).

Hydrogen-Rich Syngas Production from Gasification and Pyrolysis of Solar Dried Sewage Sludge: Experimental and Modeling Investigations

Solar dried sewage sludge (SS) conversion by pyrolysis and gasification processes has been performed, separately, using two laboratory-scale reactors, a fixed-bed pyrolyzer and a downdraft gasifier, to produce mainly hydrogen-rich syngas. Prior to SS conversion, solar drying has been conducted in order to reduce moisture content (up to 10%). SS characterization reveals that these biosolids could be appropriate materials for gaseous products production. The released gases from SS pyrolysis and gasification present relatively high heating values (up to 9.96 MJ/kg for pyrolysis and 8.02  9.96 MJ/kg for gasification) due to their high contents of H2 (up to 11 and 7 wt%, resp.) and CH4 (up to 17 and 5 wt%, resp.). The yields of combustible gases (H2 and CH4) show further increase with pyrolysis. Stoichiometric models of both pyrolysis and gasification reactions were determined based on the global biomass formula, CαHβOγNδSε, in order to assist in the products yields optimization.