This paper gives an overview of the ability of an aminomethylphosphonic acid-containing chelating resin for the removal of lithium from water. The studies were performed under various conditions, such as resin dose, initial Li + concentration, solution pH and solution temperature. The results showed that the sorption of Li + reached equilibrium within 15 min and the experimental data were well-fitted by the pseudo-second-order kinetic model. The Li + sorption was highly pH dependent, and the optimum pH for Li + removal was ≥3. Isotherm sorption data displayed good correlation with the Langmuir model, and the maximum monolayer sorption capacity of the resin found to be 13.65 mg g-1. Thermodynamic studies suggested that Li + sorption onto the chelating resin was an exothermic and spontaneous process in nature. The resin could be regenerated by 0.1 M HCl, NaCl or H 2 SO 4 with > 99 % efficiency. Desorption of Li + with 0.1 M NaCl resulted in no changes in the uptake capacity through four sequential sorption/desorption cycles.

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A numerical study of the thermohydraulics of an enhanced geothermal system project in Turkey is presented. The solid structures are modelled as porous media, using the numerically determined hydraulic fracturing data of other authors. The influence of several numerical modelling aspects such as the domain size, grid resolution, temporal resolution as well as the discretization scheme are investigated and assessed to obtain highly accurate numerical solutions under the applied modelling assumptions. Using the suggested mathematical and numerical model, different production scenarios are investigated.

The geothermal energy is a renewable and relatively clean energy resource. The amount of geothermal energy stored just in the upper crust of the earth is large enough to meet the world's energy needs for thousands of years. Unfortunately, only a small portion of this potential can be utilized today by the conventional methods. The rest corresponds to the hot, fluid-poor areas which cannot be utilized by the current technology. The first concrete steps towards the utilization of such high potential areas emerged in the late 1960s and early 1970s. These studies have gradually continued in the following years, and many new terms and conceptual designs have been proposed so far. Unfortunately, no comprehensive definition has been established on this subject yet. This may bring about some difficulties such as the failure to express the intended concept in the right manner, the inability to determine the legal boundaries for the regulations required by the countries to make use of these areas which pose high risks in the commercial point of view. In this paper, some of the major terms and conceptual designs used for the projects targeting the power generation from fluidpoor hot areas are discussed. Furthermore, all of these terms have been gathered under the title of "Unconventional Geothermal Systems-UGS" and these designs are classified according to the types of thermodynamic system for the first time in this study. In addition, some new suggestions that can be used to define the definitional boundaries of these terms are put forward.Citation info: Çiçek, A. 2020. The electric power production targeted Unconventional Geothermal Systems (UGS), some conceptual designs and their thermodynamics classification.

A comparative numerical analysis of the thermohydraulics of an enhanced geothermal system (EGS) project in Türkiye in Dikili area is presented. The fractured granodiorite is modelled as porous media, utilizing the numerically suggested data of other authors for the corresponding hydraulic characteristics. As the heat transmission fluid, two different mediums are alternatively considered. These are the more classical medium, water and the supercritical Carbon Dioxide (sCO2). Transient calculations are performed for a time period of twenty years, comparing the temporally developing results obtained for water and sCO2 with each other. Based on modeling parameters and assumptions, higher production temperatures are observed with sCO2, in comparison to water, implying an advantage for sCO2 usage as a working fluid in EGS. This is accompanied by the further advantage of a lower pressure drop for sCO2. On the other hand, the temperature advantage is relativized by the lower specific heat capacity of sCO2 causing a decrease in the production thermal power. In general, the present re found to be encouraging for a further and more detailed analysis of the employment of sCO2 as working fluid in EGS.