Gypsum is widely distributed in Tunisia occurring in the formation of Triassic age. The gypsum deposit of Mellegue is the alabastine type with a little of the porphyroblast type and contains traces of clay minerals and calcite. It is a moderately strong rock in terms of its unconfined compressive strength of 16 Mpa and tensile strength of 3.35 Mpa. Triaxial testing values indicated an apparent cohesion of 10 Mpa and an angle of friction of 26°. The gypsum studied had a percentage of SO3 of 41.71% and a percentage of CaO of 32.9%. All the samples had low densities according to the International Association of Engineering Geology (IAEG) classification and exhibited a moderate porosity whether effective or absolute. The gypsum proved to be moderately strong when tested in unconfined compression and tensile strength. Thermal analysis indicated a total weight loss of 20.27% and the whiteness index about 90%. This proved a high degree of whiteness. The time of setting can be considered short and medium, which is quite favorable for industrial application compared with other gypsum deposits currently operated.
This study aims to the initial characterization of Aptian sedimentary limestones in the Kef region located in the North-West of Tunisia in order to use in industrial fields. The limestone samples were collected from three outcrops respectively named Jebel Jerissa, Jebel Hmeima and Jebel Harraba. A geochemical characterization highlights a variation of the weight percentage (wt%) as follows: CaO (53 - 55), MgO (0.04 - 0.28), Al2O3 (0.07 - 0.51), Fe2O3 (0.41 - 2.87), and a loss on ignition (41.62 - 43.35). The other oxides (K2O, SO3, Na2O) are in trace amounts. Mineralogical analysis revealed that limestones contain more than 95% of calcite and the clay impurities are the minor phases detected. Petrographic study showed that these limestones are packestone-wakestone type. The hardness of Aptian limestones crosses the upper limit of the hard domain. Geotechnical tests reveal a Dry Micro Deval (MDS) coefficient varying from 23% to 33%, a Wet Micro Deval (MDH) coefficient with values oscillating around 26% to 36%, a Los Angeles coefficient (LA) about 25% against a value of the compressive strength ranging from 593 Kg/cm2 to 866 Kg/cm2. The gravimetric tests highlighted a flexural strength value from 106 Kg/cm2 at 208 Kg/cm2, while the ultrasonic coefficient oscillates from 4876 m/s to 5233 m/s, indicating the low porosity of these limestone (0.5% to 1%). The density recorded an average value of 2.50 g/cm3. The various properties studied have proved that the limestone studied can be used in various industrial fields such steel industry, aggregate, cement industry and marble.
This study focused on the geochemical, mineralogical and technological characterization of clays in Makthar area (Central of Tunisia) of Cretaceous-Paleogene. Its aims are to identify and promote use in the field of ceramics industry. The result of the mineralogical analysis of clays showed a dominance of illite with a percentage higher than 65%, of kaolinite and smectite with percentages of 15%. Geochemical analysis of the major elements of clay showed a SiO2 content exceeding 29% and a percentage of Al2O3 higher than 7.5%. The Fe2O3 percentage was ranging from 3% to 8%. The percentage of CaO was between 22.5% and 28% while that of K2O is 4%. The percentages of SO4, MgO and NaO2 were in very small fractions. Granulometric and microgranulometric analysis showed that the clay fraction (2/g to 178 m2/g reflecting illite dominance. Drying behavior indicated that clay mixture had a drying shrinkage less than 7%, while the firing shrinkage didn’t exceed 2% giving the possibility of clay using in the ceramics field.
This work aims to assess the effect of energy conversion (Thermal oil, Natural gas and cogeneration system) on atmospheric emission and energy consumption in ceramic tile product sector in Tunisia. Two tile manufactures were selected. The first plant has two production lines: The first line (FF1) operates with thermal oil with a lower calorific value (LHV) of 9811 cal/g and the second line (FG1) operating with natural gas has a lower calorific value (HHV) of 10,520 cal/g, ensuring a daily output of 300 tons each one. The second manufacture (SC2) operates with natural gas with the same LHV value. The thermal oil energy balance showed a specific consumption of 0.0481 toe/ton tile product for the FF1 manufacture line, 0.0198 toe/ton of tile product for the FG1 manufacture line and 0.0143 toe/ton of tile product for the SC2 manufactory. The electrical energy consumption was 0.0121 toe/ton of tile product for the FF1 line, 0.0108 toe/ton of tile product for the FG1 line and a production of energy (exergy) of 0.014 toe/ton for the SC2 production line. The specific consumption was split into 40% for dryer and 60% for tunnel kilns. The conversion allow to record a dryer reduction rate of 80% for nitrogen oxides (NOx), 56% for sulfur oxides (SOx), 56% for fluorinated compounds, 52% for chlorinated compounds and 52% for volatile organic compound. Whereas, the kiln reduction rate was 36% for nitrogen oxides, 51% for sulfur oxides, 36% for chlorinated compounds and 55% for fluorinated and 50% for volatile organic compounds (VCOs). Compared to natural gas line, the use of cogeneration system in kiln process shows a decrease of 67% for NOx emissions, 80% for SOx emissions, 89% for fluorinated compounds, 58% for chlorinated emissions and 64% for volatiles organic compounds. Compared to thermal oil, the use of cogeneration system reduces the thermal energy consumption by 70% and allowed to save 30% of electric energy by generate 20% of needed electric energy. The specific atmospheric gaseous emission level decrease from 2.066 g/kg of tile product for the thermal oil process to reach 0.43 g/kg of tile product for cogeneration process.
