Jale Gülen

Thermal analysis of borogypsum and its effects on the physical properties of Portland cement

Borogypsum, which consists mainly of gypsum crystals, B2O3 and some impurities, is formed during the production of boric acid from colemanite, which is an important borate ore. In this study, the effect of borogypsum and calcined borogypsum on the physical properties of ordinary Portland cement (OPC) has been investigated. The calcination temperature and transformations in the structures of borogypsum and natural gypsum were determined by differential thermal analysis (DTA), thermogravimetric analysis (TGA) and X-ray diffraction (XRD) techniques. Thermal experiments were carried out between ambient temperature and 500 °C in an air atmosphere at a heating rate of 10 °C min−1. After calculation of enthalpy and determination of conversion temperatures, borogypsum (5% and 7%), hemihydrate borogypsum (5%) and natural gypsum (5%) were added separately to Portland cement clinker and cements were ground in the laboratory. The final products were tested for chemical analysis, compressive strength, setting time, Le Chatelier expansion and fineness properties according to the European Standard (EN 196). The results show that increasing the borogypsum level in Portland cement from 5% to 7% caused an increase in setting time and a decrease in soundness expansion and compressive strength. The cement prepared with borogypsum (5%) was found to have similar strength properties to those obtained with natural gypsum, whereas a mixture containing 5% of hemihydrate borogypsum was found to develop 25% higher compressive strength than the OPC control mixtures at 28 days. For this reason, utilization of calcined borogypsum in cement applications is expected to give better results than untreated borogypsum. It is concluded that hemihydrate borogypsum could be used as a retarder for Portland cement as an industrial side. This would play an important role in reducing environmental pollution.

Removal of Mineral Matter from Silopi-Harput Asphaltite by Acid Treatment

The surface properties of fossil fuel show differences according to ranks and mineral matter content. The fossils that have high mineral matter content are treated with some applications before using. This is a kind of enrichment. This process is helpful to both economic and technological points of view. The mineral matter of fossil can be decreased by chemical demineralization. The main purpose of demineralization is to seperate the mineral matter without changing the organic structure. In this study, demineralization was studied using different acids (HCl, H 2 SO 4 and HNO 3 ) at various concentrations. Maximum demineralization degree (approximately 40%) was found of asphaltite sample leaching with 5 and 10% HCl acids. FTIR and XRD were used to determine the functional groups of treated sample and the contents of ash, respectively.

Mineral Matter Identification in Nallıhan Lignite by Leaching with Mineral Acids

Abstract Coals are heterogeneous, complex noncrystalline macromolecules having both organic and inorganic materials that contain some inorganic constituents. Some techniques have been applied to this fossil fuel in order to remove these undesired inorganic parts from the organic part. Chemical demineralization is one of the suitable methods for removal of inorganic elements although it is an expensive way. But by this method, many elements are leached effectively from the lignite body from the point of economic view because these inorganic parts may cause some undesired deleterious effects. In this study, the demineralization effect of some aqueous acids of 5% such as HCl, H2SO4, HNO3, and HF was studied. The effect of these mineral acids was shown by X-ray spectroscopy.

The Effects of Temperature and Mineral Acids on the Demineralization Degree of Nallihan Lignite

Demineralization of lignites from Nallihan, Turkey, was investigated using various aqueous acids, such as HCl, HNO3, and H2SO4, which were used at the concentrations of 5 and 10 vol%, hydrofluoric acid (HF) acid solutions of 5, 10, 20, 30, and 40 vol%. The experiments were done at 20, 40, 50, and 60°C temperatures in order to observe the heating effect on the removal yields. The best result was found for the sample being done experimentally with 5% HF. The ash content is decreased from 17.12 to 6.98 wt% and heating value is increased from 16,652 to 23,950 kJ/kg according to the original lignite. The yields are 59.23 and 44%, respectively. Fourier transform infrared and X-ray diffraction were used to observe the leaching effect of the mineral acids on the demineralization degree of Nallihan lignite.

The Effect of Aqueous Caustic and Various Acid Treatments on the Removal of Mineral Matter in Asphaltite

Abstract In this present study, high mineral matter (ash) asphaltites from Silopi, Southeastern Anatolia, Turkey were investigated using aqueous sodium hydroxide followed by various mineral acids such as HNO3, HCl, H2SO4, and HF. The extraction with 5% NaOH followed by leaching with 10% H2SO4 plus 40% HF was the optimum approach for chemical cleaning of the asphaltite and the maximum degree of the demineralization was found as 59.56%. At the same time, the calorific value increased to 20.86% according to the original sample. In addition, the spectrometric analyses of treated asphaltite samples were performed by FTIR and X-ray diffraction.

Removal of amitraz from aqueous solutions on clay by adsorption technique at industrial scale

Abstract Amitraz (AZ) that is used as acaricide was extracted by using clay adsorbent. The experimental data were modeled via Langmuir and Freundlich isotherms in which adsorption data fit well. The monolayer adsorption capacity was found as 28.53 mg × g−1 at a temperature of 30 °C. The effects of the phases contact time, the initial solution pH value and the initial pesticide concentration were investigated regarding the points of adsorption equilibrium and yield. The adsorption kinetics were investigated by applying pseudo-first-order, pseudo-second-order and intra-particle diffusion laws. Adsorption of AZ was found to be best fitted by the pseudo-second-order model. The intra-particle diffusion also plays an important role in adsorption phenomenon. This adsorption is a physical and spontaneous phenomenon. The pesticide removal by adsorption technique was successfully applied in industrial plants.

Potential Methods for Converting Coal into Gasification Products for Reduced Global Warming

Turkey has huge lignite reserves although they have high ash, sulfur, and volatile matter. The direct usage of this fossil fuel has disadvantages such as fouling, acid rains, greenhouse gases (GHGs), etc. Greenhouse gases are the principal factor for global warming and climate change. Some gasification processes can be applied for turning coal into valuable products such as water gas, producer gas or synthetic natural gas. The undesired parts of coal that cause the pollution in the environment can be removed for increasing the fuel quality. This can be managed by physical and chemical methods or both of them.

Effect of Oxidative Medium on Removal of Sulfur and Mineral Matter from the Can Lignites

Environmental problems associated with energy use consist of an increasing spectrum of pollutants, hazards, accidents, and degradation of environmental quality and natural ecology (Dincer, 1998). Climate change is threatening human beings on the world. Earthquakes, typhoons, cyclones, floods are the common natural disasters for all of us because of the seasonal variations. The industrilialized countries are mainly responsible for air pollution, ozone depletion, and carbon emissions due to the small contribution of developing countries (Dincer, 1998). Increased emissions of greenhouse gases from human activities are the main reason for this situation. In these days, acid rains, energy requirement, greenhouse gas effect, etc., are global problems for human beings.