Thermodynamic and Kinetic Modelling of Scales Formation at the Soultz-sous-Forêts Geothermal Power Plant

Geothermal energy has been a subject of great interest since the 1990s in the Upper Rhine Graben (URG), where the first European Enhanced Geothermal System (EGS) pilot site has been developed, in Soultz-sous-Forêts (SsF), France. Several studies have already been conducted on scales occurring at the reinjection side at the geothermal plants located in the URG. It has been observed that the composition of the scales changes as chemical treatment is applied to inhibit metal sulfate. The purpose of this study was to model the scaling phenomenon occurring in the surface pipes and the heat exchangers at the SsF geothermal plant. PhreeqC, a geochemical modelling software, was used to reproduce the scaling observations in the geothermal plant during exploitation. A suitable database was chosen based on the availability of chemical elements, minerals, and gas. A thermodynamic model and a kinetic model were proposed for modelling the scaling phenomenon. The thermodynamic model gave insight on possible minerals precipitated while the kinetic model, after modifying the initial rates equation, produced results that were close to the expected scale composition at the SsF geothermal plant. Additional laboratory studies on the kinetics of the scales are proposed to complement the current model.

Convenient Agarose Preparation with Hydrogen Peroxide and Desulfation Process Analysis

Agarose is a natural seaweed polysaccharide and widely used in the medicine, food, and biological fields because of its high gel strength, non-toxicity, and electrical neutrality. The sulfate group is one of the main charged groups that affect the performance of agarose. In the present study, a simple, eco-friendly, and efficient method was explored for agarose preparation. After desulfation with hydrogen peroxide (H2O2), the sulfate content of agar reached 0.21%. Together with gel strength, electroendosmosis, gelling and melting temperature, the indicators of desulfated agar met the standards of commercially available agarose. Notably, the desulfated agar can be used as an agarose gel electrophoresis medium to separate DNA molecules, and the separation effect is as good as that of commercially available agarose. Further, the H2O2 desulfation process was analyzed. The addition of a hydroxyl radical (HO•) scavenger remarkably decreased the H2O2 desulfation rate, indicating that HO• has a certain role in agar desulfation. Sulfate content detection indicated that sulfur was removed from agar molecules in the form of sulfate ions (SO42−) and metal sulfate. The band absence at 850 cm−1 indicated that the sulfate groups at C-4 of D-galactose in sulfated galactan were eliminated.

Deep-ultraviolet transparent alkali metal-rare earth metal sulfate NaY(SO4)2.H2O as a nonlinear optical crystal: synthesis and characterization

A new alkali metal-rare earth metal sulfate with the formula NaY(SO4)2.H2O has been synthesized using a mild hydrothermal method. It crystallizes in the noncentrosymmetric trigonal space group P3121 (No. 152)...

A general approach to reaching perovskite nanocrystals with insulating metal sulfate shells

The strategy of constructing core/shell structure is of great importance for emitting semiconductor nanocrystals. However, the coating on soft metal halide perovskite nanocrystals at the single particle level remains a...

Rb3In(SO4)3: a Defluorinated Mixed Main-Group Metal Sulfate for Ultraviolet Transparent Nonlinear Optical Material with Large Optical Band Gap

Ultraviolet (UV) nonlinear optical (NLO) materials possess important practical applications in modern laser science and technology, which are attracting significant research interest in the fields of chemistry, physics and materials...

The anti-wear enhancement of boric acid + molybdenum disulfide derived tribofilm

Additives are important components to reduce friction and wear of tribological systems. Zinc dithiophosphate (ZDDP), the most commonly used anti-wear additive prevents the tribological system from the friction and wear loss without any commercially available antagonist additive. However, its environmentally harmful content enforces to lubricating oil manufacturers to replace it with an alternative one. Therefore, in this study, the H3BO3 + MoS2 combination was tested in the boundary lubrication regime in a tribometer with a pin on flat reciprocating test module to be a possible alternative anti-wear additive against ZDDP. The friction and wear behavior of Boric acid (H3BO3) + Molybdenum Disulfide (MoS2), ZDDP, MoS2, and H3BO3 evaluated in terms of friction coefficient (COF), wear rate, surface energy and tribo-chemical analysis of tribofilms. SEM/EDX and XPS were employed to explore tribofilm formations on the wear scars. According to the results, the addition of MoS2 into H3BO3 presented a similar tribological performance to ZDDP by forming a strength tribofilm on the surface containing B2O3, MoO3, and metal sulfate.

High Temperature Pressure Oxidation of a Low-Grade Nickel Sulfide Concentrate with Control of the Residue Composition

High temperature pressure oxidation of a low-grade nickel concentrate was examined to demonstrate the potential benefits and shortcomings of this approach. The high iron sulfide content ensured that acid generation was much greater than for higher grade concentrates. This results in the formation of basic iron sulfate phases and a significant amount of sulfuric acid. Kinetic sampling during pressure oxidation tests also demonstrated the transformation of sulfide minerals, including the oxidative transformations of pentlandite to violarite and then to vaesite, the latter phase not previously noted in studies of this kind. Finally, addition of a divalent metal sulfate buffer, here magnesium sulfate, mitigates the formation of basic iron sulfates but with greater generation of sulfuric acid in the leach liquor. Under the conditions employed in this study, this acid could be employed to leach other nickel-containing materials such as nickel laterites.

Sulfur Conversion of Mixed Coal and Gangue during Combustion in a CFB Boiler

The construction of a power plant using a 660 MWe supercritical circulating fluidized bed (CFB) boiler with co-combustion of coal and gangue has been proposed in China. Therefore, this study simulated the distribution law and transformation mechanism of sulfur-containing phases using three low-calorific samples of gangue and coal mixtures under different conditions, based on the thermodynamic simulation software HSC Chemistry. The results showed that sulfur low in calorific value coal is mainly converted into gas phase SO2, solid phase alkali metal sulfate (Na2SO4 and K2SO4), and alkaline earth metal sulfate (CaSO4 and MgSO4) in an oxidizing atmosphere. Under a reductive atmosphere, sulfur in coal is mainly converted into gaseous H2S, COS (Carbon oxysulfide), and solid FeSx. With an increase in the O/C ratio, the distribution curve of sulfur-containing substances contracted to lower temperatures. It was established that the sulfur fixation capacity of coal ash depends on the relative amounts of basic oxides and sulfur present in it. Relevant conclusions were also verified and compared to those of the laboratory small-fluidized bed test bench and the 3 MWth CFB combustion test bench.