EDF R&D Lab Chatou, 6 quai Watier, 78400 Chatou, France.
EDF R&D Lab Chatou, 6 quai Watier, 78400 Chatou, France.
Ultrason Sonochem. 2018 Jul;45:17-28. doi: 10.1016/j.ultsonch.2018.02.044. Epub 2018 Mar 6.
CO capture and utilization (CCU) is a process that captures CO emissions from sources such as fossil fuel power plants and reuses them so that they will not enter the atmosphere. Among the various ways of recycling CO, reduction reactions are extensively studied at lab-scale. However, CO reduction by standard methods is difficult. Sonochemistry may be used in CO gas mixtures bubbled through water subjected to ultrasound waves. Indeed, the sonochemical reduction of CO in water has been already investigated by some authors, showing that fuel species (CO and H) are obtained in the final products. The aim of this work is to model, for a single bubble, the close coupling of the mechanisms of bubble dynamics with the kinetics of gas phase reactions in the bubble that can lead to CO reduction. An estimation of time-scales is used to define the controlling steps and consequently to solve a reduced model. The calculation of the concentration of free radicals and gases formed in the bubble is undertaken over many cycles to look at the effects of ultrasound frequency, pressure amplitude, initial bubble radius and bubble composition in CO. The strong effect of bubble composition on the CO reduction rate is confirmed in accordance with experimental data from the literature. When the initial fraction of CO in the bubble is low, bubble growth and collapse are slightly modified with respect to simulation without CO, and chemical reactions leading to CO reduction are promoted. However, the peak collapse temperature depends on the thermal properties of the CO and greatly decreases as the CO increases in the bubble. The model shows that initial bubble radius, ultrasound frequency and pressure amplitude play a critical role in CO reduction. Hence, in the case of a bubble with an initial radius of around 5 μm, CO reduction appears to be more favorable at a frequency around 300 kHz than at a low frequency of around 20 kHz. Finally, the industrial application of ultrasound to CO reduction in water would be largely dependent on sonochemical efficiency. Under the conditions tested, this process does not seem to be sufficiently efficient.
CO 捕集与利用（CCU）是一种从化石燃料电厂等源头捕获 CO 排放物并加以再利用，以防止其进入大气的过程。在 CO 再循环的各种方法中，还原反应在实验室规模上得到了广泛研究。然而，用标准方法还原 CO 较为困难。声化学可能用于在水中鼓泡的 CO 气体混合物，使其在超声波的作用下发生还原反应。实际上，一些作者已经研究了 CO 在水中的声化学还原，表明在最终产物中获得了燃料物种（CO 和 H）。本工作的目的是为单个气泡建模，将气泡动力学机制与气泡中气相反应动力学紧密耦合，从而实现 CO 还原。通过估计时间尺度来定义控制步骤，进而求解简化模型。通过对许多周期内气泡中自由基和气体的浓度进行计算，研究了超声频率、压力振幅、初始气泡半径和 CO 初始组成对 CO 还原的影响。计算结果与文献中的实验数据一致，证实了气泡组成对 CO 还原速率的强烈影响。当气泡中 CO 的初始分数较低时，与无 CO 模拟相比，气泡的生长和破裂略有变化，促进了导致 CO 还原的化学反应。然而，峰值破裂温度取决于 CO 的热性质，随着气泡中 CO 含量的增加而大大降低。模型表明，初始气泡半径、超声频率和压力振幅在 CO 还原中起着关键作用。因此，在初始半径约为 5 µm 的气泡的情况下，CO 还原在 300 kHz 左右的频率下似乎比在 20 kHz 左右的低频下更为有利。最后，在水中利用超声进行 CO 还原的工业应用将在很大程度上取决于声化学效率。在测试的条件下，该过程似乎效率不高。
