Kaouther Zaafouri

Enhancement of biofuels production by means of co-pyrolysis of Posidonia oceanica (L.) and frying oil wastes: Experimental study and process modeling.

Energy recovery from lignocellulosic solid marine wastes, Posidonia oceanica wastes (POW) with slow pyrolysis responds to the growing trend of alternative energies as well as waste management. Physicochemical, thermogravimetric (TG/DTG) and spectroscopic (FTIR) characterizations of POW were performed. POW were first converted by pyrolysis at different temperatures (450°C, 500°C, 550°C and 600°C) using a fixed-bed reactor. The obtained products (bio-oil, syngas and bio char) were analyzed. Since the bio-oil yield obtained from POW pyrolysis is low (2wt.%), waste frying oil (WFO) was added as a co-substrate in order to improve of biofuels production. The co-pyrolysis gave a better yield of liquid organic fraction (37wt.%) as well as syngas (CH4,H2…) with a calorific value around 20MJ/kg. The stoichiometric models of both pyrolysis and co-pyrolysis reactions were performed according to the biomass formula: CαHβOγNδSε. The thermal kinetic decomposition of solids was validated through linearized Arrhenius model.

Hydrogen-rich syngas production from pyrolysis and gasification of palmitic fibers

Pyrolysis and gasification are two attractive processes for converting pre-dried palmitic fibers (PF) into valuable gaseous products with high effectiveness and little environmental impact. The gasification and pyrolysis of pre-dried PF were conducted independently, using two different laboratory-scale fixed-bed reactors. The key properties of produced biofuels - and mainly of gaseous ones - obtained from both thermochemical processes have been investigated. The raw material characterization reveals that the pre-dried PF are suitable feedstock for thermochemical conversion and mainly for syngas production. The reactor temperature distribution was between 600 and 1000°C for gasification process and between 400 and 600°C for pyrolysis. Gasification and pyrolysis of pre-dried PF produce high-quality combustible gases (syngas), formed mainly of CO, H2, CO2, N2, CH4 and CnHm, that can be used either as a fuel to produce heat and power or as an intermediate in the production of liquid fuels and chemicals. However, the syngas specifications requested for most of these applications require important upgrading operations that enhance considerably the energy efficiency.

Feasibility of a Bioremediation Process Using Biostimulation with Inorganic Nutrient NPK for Hydrocarbon Contaminated Soil in Tunisia

This study focused on the processing time reduction of soils microcosm process, during the biological restore ofxa0diesel-contaminated soil under natural conditions. Biodegradation activity of hydrocabonoclastic microflora andxa0biostimulation with inorganic nutrient (NPK) were studied through the determination of optimal conditions whichxa0improve bioremediation process. Indeed, after 56 days, about 98% removal rate of total petroleum hydrocarbonxa0(TPH) in soil treated by microcosm’s technique were observed relative to approximately 2.22×107CFU/g soil ofxa0bacterial number. This performance was achieved with microbial (bacteria) metabolism which accompaniesxa0biodegradation of hydrocarbons. Moreover, the hydrocarbon fractions (alkanes and aromatics) were rapidly degraded then the other complex fractions according to GC/MS and FT-IR analysis

Optimization of Hydrothermal and Diluted Acid Pretreatments of Tunisian Luffa cylindrica (L.) Fibers for 2G Bioethanol Production through the Cubic Central Composite Experimental Design CCD: Response Surface Methodology

This paper opens up a new issue dealing with Luffa cylindrica (LC) lignocellulosic biomass recovery in order to produce 2G bioethanol. LC fibers are composed of three principal fractions, namely, α-cellulose (45.80%u2009u2009± 1.3), hemicelluloses (20.76%u2009u2009± 0.3), and lignins (13.15%u2009u2009± 0.6). The optimization of LC fibers hydrothermal and diluted acid pretreatments duration and temperature were achieved through the cubic central composite experimental design CCD. The pretreatments optimization was monitored via the determination of reducing sugars. Then, the 2G bioethanol process feasibility was tested by means of three successive steps, namely, LC fibers hydrothermal pretreatment performed at 96°C during 54 minutes, enzymatic saccharification carried out by means of a commercial enzyme AP2, and the alcoholic fermentation fulfilled with Saccharomyces cerevisiae. LC fibers hydrothermal pretreatment liberated 33.55u2009g/kg of reducing sugars. Enzymatic hydrolysis allowed achieving 59.4u2009g/kg of reducing sugars. The conversion yield of reducing sugar to ethanol was 88.66%. After the distillation step, concentration of ethanol was 1.58% with a volumetric yield about 70%.

Pyrolysis of Date palm waste in a fixed-bed reactor: Characterization of pyrolytic products

The pyrolysis of several Tunisian Date Palm Wastes (DPW): Date Palm Rachis (DPR), Date Palm Leaflets (DPL), Empty Fruit Bunches (EFB) and Date Palm Glaich (DPG) was run using a fixed-bed reactor, from room temperature to 500°C, with 15°C/min as heating rate and -5°C as condensation temperature, in order to produce bio-oil, biochar and syngas. In these conditions, the bio-oil yield ranges from 17.03wt% for DPL to 25.99wt% for EFB. For the biochar, the highest yield (36.66wt%) was obtained for DPL and the lowest one (31.66wt%) was obtained from DPG while the syngas production varies from 39.10wt% for DPR to 46.31wt% DPL. The raw material and pyrolysis products have been characterized using elemental analysis thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM). The syngas composition has been characterized using gas analyzer.

Evaluation of the Efficiency of Ethanol Precipitation and Ultrafiltration on the Purification and Characteristics of Exopolysaccharides Produced by Three Lactic Acid Bacteria

Exopolysaccharides (EPS) produced by three Lactic Acid Bacteria strains, Lactococcus lactis SLT10, Lactobacillus plantarum C7, and Leuconostoc mesenteroides B3, were isolated using two methods: ethanol precipitation (EPS-ETOH) and ultrafiltration (EPS-UF) through a 10 KDa cut-off membrane. EPS recovery by ultrafiltration was higher than ethanol precipitation for Lactococcus lactis SLT10 and Lactobacillus plantarum C7. However, it was similar with both methods for Leuconostoc mesenteroides B3. The monomer composition of the EPS fractions revealed differences in structures and molar ratios between the two studied methods. EPS isolated from Lactococcus lactis SLT10 are composed of glucose and mannose for EPS-ETOH against glucose, mannose, and rhamnose for EPS-UF. EPS extracted from Lactobacillus plantarum C7 and Leuconostoc mesenteroides B3 showed similar composition (glucose and mannose) but different molar ratios. The molecular weights of the different EPS fractions ranged from 11.6±1.83 to 62.4±2.94u2009kDa. Molecular weights of EPS-ETOH fractions were higher than those of EPS-UF fractions. Fourier transform infrared (FTIR) analysis revealed a similarity in the distribution of the functional groups (O-H, C-H, C=O, -COO, and C-O-C) between the EPS isolated from the three strains.

Sewage Sludge as Source of Energy: Experimental and Numerical Investigations of Thermochemical Conversion of Sewage Sludge via Pyrolysis

This study is mainly devoted to the energetic conversion of Tunisian sewage sludge (SS) into second generation biofuels (bio-oil, syngas and bio-char) using pyrolysis process. In fact, urban wastewater treatment operations has generated increasingly large quantities of sewage sludge (SS) (around 2 million tons/year in 2009, ONAS 2010) in Tunisia, since 1974—date of implementation of the first wastewater treatment plants (WWTP).

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 9.96u2009MJ/kg for pyrolysis and 8.02u2009u20099.96u2009MJ/kg for gasification) due to their high contents of H2 (up to 11 and 7u2009wt%, resp.) and CH4 (up to 17 and 5u2009wt%, 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.