The expanding geothermal energy sector still faces performance issues due to scalings in pipes and surface level installations, which require elevated operation pressure levels and costly maintenance. For facilities in the North Alpine Foreland Basin, the precipitation of $${\hbox {CaCO}}_{3}$$ is the main problem which is a consequence of the disruption of the lime-carbonic acid equilibrium during production. The formation of gas bubbles plays a key role in the scaling process. This work presents experiments in a bubble column to quantify the effects of gas stripping on carbonate precipitation and an extension of PhreeqC to include kinetic exchange between a gas phase and water for the simulation of the experimental results. With the same hybrid model not only precipitation of $${\hbox {CaCO}}_{3}$$ but also the dissolution of scalings by the injection of $${\hbox {CO}}_{2}$$ could be quantified. The bubble column was filled with tap water and brine. By varying the ionic strength of the solution, a wider range of geothermal waters was covered. Air and $${\hbox {CO}}_{2}$$ were introduced at the bottom. The precipitates built on the column wall were analyzed with Raman spectroscopy: injecting air into tap water at low ionic strength led to the formation of aragonite with 59.8% of the precipitates remaining at the column wall and the rest as particles in dispersion. At moderate ionic strength the dominant polymorph was calcite and 81.5% of the crystals were attached to the wall. At high ionic strength precipitation was inhibited. The presence of crystallization nuclei reduced the time for precipitation, but not the amount of scalings formed. Injecting $${\hbox {CO}}_{2}$$ into the solution completely removed the scalings from the column wall. The model and its experimental backup lay the foundation for a process-based prediction of the scales (not only) in geothermal systems.

中文翻译：

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气水平衡对碳酸盐沉淀影响的量化

不断扩大的地热能行业仍然面临着性能问题，原因是管道和地面安装结垢，这需要更高的运行压力水平和昂贵的维护费用。对于北高山前陆盆地的设施，$${\hbox {CaCO}}_{3}$$ 的沉淀是主要问题，这是生产过程中石灰-碳酸平衡被破坏的结果。气泡的形成在结垢过程中起着关键作用。这项工作介绍了在气泡塔中进行的实验，以量化气提对碳酸盐沉淀的影响，并扩展了 PhreeqC 以包括气相和水之间的动力学交换，以模拟实验结果。使用相同的混合模型，不仅可以沉淀 $${\hbox {CaCO}}_{3}$$，还可以通过注入 $${\hbox {CO}}_{2}$$ 溶解水垢被量化。气泡柱充满自来水和盐水。通过改变溶液的离子强度，可以覆盖范围更广的地热水。底部引入了空气和 $${\hbox {CO}}_{2}$$。用拉曼光谱分析柱壁上形成的沉淀物：在低离子强度下将空气注入自来水中导致文石的形成，其中 59.8% 的沉淀物保留在柱壁上，其余为分散的颗粒。在中等离子强度下，主要多晶型物是方解石，81.5% 的晶体附着在壁上。在高离子强度沉淀被抑制。结晶核的存在减少了沉淀时间，但不减少形成的水垢量。将 $${\hbox {CO}}_{2}$$ 注入溶液中，完全去除了塔壁上的结垢。该模型及其实验备份为基于过程的地热系统规模（不仅）预测奠定了基础。