We report the discovery of novel regimes of calcium carbonate dissolution in micron-scale confined spaces through microfluidic experiments. In the experiments, hydrochloric acid is injected into a microfluidic chamber with pre-deposited calcium carbonate solids. As the acid flow rate is decreased, the dissolution of calcium carbonate transits from a liquid/solid single-phase reactive transport regime to a gas/liquid/solid two-phase one. The two-phase regime further splits into two different regimes, one with fluctuating and the other with nonfluctuating gaseous CO₂ phase. We name the three regimes as “Nongaseous”, “Gaseous Breathing”, and “Gaseous Nonbreathing”. The experimental observations are reproduced and interpreted by mathematical modeling. Results show that the regimes are controlled by the ratio of H⁺ concentration and saturated CO₂ concentration, the Peclet number and the second Damkohler number. Dimensionless diagrams distinguishing different regimes are presented and an empirical relationship is proposed. Our results offer insights into various engineering and natural processes, e.g., geological carbon storage, petroleum reservoir acidizing, Karst dissolution, and others that are governed by small scale multiphase reactive flow physics.

我们通过微流体实验报告了在微米级密闭空间中发现碳酸钙溶解的新机制。在实验中，将盐酸注入具有预沉积碳酸钙固体的微流体室中。随着酸流速的降低，碳酸钙的溶解从液/固单相反应传输状态转变为气/液/固两相状态。两相状态进一步分成两种不同的状态，一种具有波动的气态CO 2 相，而另一种具有非波动的气态CO ₂相。我们将这三种状态命名为“非气态”、“气态呼吸”和“气态非呼吸”。通过数学模型再现和解释实验观察结果。结果表明，这些制度是由 H 的比率控制的⁺浓度和饱和 CO ₂浓度、Peclet 数和第二 Damkohler 数。提出了区分不同制度的无量纲图，并提出了经验关系。我们的结果提供了对各种工程和自然过程的见解，例如地质碳储存、石油储层酸化、岩溶溶解以及其他受小规模多相反应流物理控制的过程。