“Blue energy” could be produced by exploiting the large salinity gradient between geothermal fluids and freshwater through a SaltPower system. This study is an attempt to select the most favorable chemicals to avoid injectivity issues when a diluted geothermal fluid resulting from the SaltPower system is returned to the reservoir. Three synthetic chelating agents (oxalic acid, EDTA, and EDDS) and one natural (humic acid) were evaluated through speciation simulations and isothermal titration calorimetry (ITC) experiments. The speciation simulation results indicate that the degree of complexing is highly dependent on pH and chelating agent type. The ITC experiments show that the total heat for the formation of soluble metal–ligand complexes in the rock + geothermal brine system follows: EDTA > EDDS > oxalic acid > humic acid. The simulations and calorimetry results suggest that EDTA could be used to avoid the precipitation of Fe(III) oxides and other minerals (e.g., calcite and dolomite) inside the porous media upon the reinjection of diluted geothermal brine coming from SaltPower electricity production.

中文翻译：

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稀释地热盐水回注用螯合剂

通过 SaltPower 系统利用地热流体和淡水之间的大盐度梯度可以产生“蓝色能源”。本研究试图选择最有利的化学品，以避免在 SaltPower 系统产生的稀释地热流体返回储层时出现注入问题。通过形态模拟和等温滴定量热法 (ITC) 实验对三种合成螯合剂（草酸、EDTA 和 EDDS）和一种天然螯合剂（腐殖酸）进行了评估。形态模拟结果表明，络合程度高度依赖于 pH 值和螯合剂类型。ITC实验表明，岩石+地热盐水系统中形成可溶性金属-配体配合物的总热量如下：EDTA > EDDS > 草酸 > 腐殖酸。模拟和量热结果表明，在重新注入来自 SaltPower 发电的稀释地热盐水时，EDTA 可用于避免多孔介质内 Fe(III) 氧化物和其他矿物质（例如方解石和白云石）的沉淀。