Analysis of calcium carbonate scaling and antiscaling field experiment

Calcium carbonate precipitation is a common problem in geothermal industry, which dramatically hampers geothermal development and also increases maintenance costs. To solve such a problem, here the whole process of scaling and antiscaling, including scaling type analysis, scaling process simulation, flashing point determination, antiscaling equipment design, inhibitor selection, antiscaling experiment and inhibition efficiency evaluation is investigated. The results show that the flashing point can be calculated by a mathematical model using wellhead and well bottom parameters. Chemical inhibitors injected into brine below the flashing point can effectively solve the problem of calcium carbonate precipitation, obtaining an inhibition efficiency of 89.37% with an inhibitor concentration of 25.61 ppm

Experimental Study on the Distribution Characteristics of CO2 in Methane Hydrate-Bearing Sediment during CH4/CO2 Replacement

CH4/CO2 replacement is of great significance for the exploitation of natural gas hydrate resources and CO2 storage. The feasibility of this method relies on our understanding of the CH4/CO2 replacement efficiency and mechanism. In this study, CH4/CO2 replacement experiments were carried out to study the distribution characteristics of CH4 and CO2 in hydrate-bearing sediments during and after replacement. Similar to previously reported data, our experiments also implied that the CH4/CO2 replacement process could be divided into two stages: fast reaction and slow reaction, representing CH4/CO2 replacement in the hydrate-gas interface and bidirectional CH4/CO2 diffusion caused replacement, respectively. After replacement, the CO2 content gradually decreased, and the methane content gradually increased with the increase of sediment depth. Higher replacement percentage can be achieved with higher replacement temperature and lower initial saturation of methane hydrate. Based on the calculation of CO2 consumption amounts, it was found that the replacement mainly took place in the fast reaction stage while the formation of CO2 hydrate by gaseous CO2 and water almost runs through the whole experimental process. Thus, the pore scale CH4/CO2 replacement process in sediments can be summarized in the following steps: CO2 injection, CO2 diffusing into sedimentary layer, occurrence of CH4/CO2 replacement and CO2 hydrate formation, wrapping of methane hydrate by mixed CH4-CO2 hydrate, continuous CO2 hydrate formation, and almost stagnant CH4/CO2 replacement

Highly Selective and Rapid Uptake of Radionuclide Cesium Based on Robust Zeolitic Chalcogenide via Stepwise Ion-Exchange Strategy

The safe use of nuclear energy requires the development of advanced adsorbent technology to address environment damage from nuclear waste or accidental release of radionuclides. Recently developed amine-directed chalcogenide frameworks have intrinsic advantages as ion-exchange materials to capture radionuclides, because their exceptionally negative framework charge can lead to high cation-uptake capacity and their 3-D multidimensional intersecting channel promotes rapid ion diffusion and offer a unique kinetic advantage. Prior to this work, however, such advantages could not be realized because organic cations in the as-synthesized materials are sluggish during ion exchange. Here we report an ingenious approach on the activation of amine-directed zeolitic chalcogenides through a stepwise ion-exchange strategy and their use in cesium adsorption. The activated porous chalcogenide exhibits highly enhanced cesium uptake compared to the pristine form and is comparable to the best metal chalcogenide sorbents so far. Further ion-exchange experiments in the presence of competing ions confirm the high selectivity for cesium ions. Excellent removal performance has also been observed in real water samples, highlighting the importance of stepwise ion exchange strategy to activate amine-directed chalcogenide framework for ¹³⁷Cs⁺ removal