This work presents an experimental study of an electrochemical regenerator for stripping CO₂ and recovering potassium hydroxide from potassium carbonate/bicarbonate streams. This regenerator is applicable in the regenerative step of an aqueous Direct Air Capture (DAC) process during which CO₂ is captured from air using potassium hydroxide. Experimental tests were conducted in a near zero-gap cell designed with nickel foam electrodes to show CO₂ stripping from carbon-loaded streams, investigating the effects of current, flowrate, and concentration of anolyte and catholyte, on the performance of the electrochemical regenerator in terms of the CO₂ stripping efficiency (CSE) and energy consumption (EC). Results from the tests show that about 90 percent of the CSE is achievable in this process with a mixture of 0.15 M potassium carbonate and 0.15 M potassium bicarbonate as the feed stream at potassium factor, $k_f,$$k_f,$ of ∼1, whereby decreasing the alkalinity to carbon ratio can further boost the CSE under the same current density. The study shows that increasing the potassium factor favors the CSE, while increasing the buffering factor has a negative impact on the CSE. Furthermore, for potassium factors below the “buffering threshold”, the CSE is negligible. Results also show that the CSE is constant for varying applied current at constant potassium factor. In addition, the influence of supporting electrolyte (SEL) in the cathode chamber of the regenerator, on both the CSE and the voltage penalty is studied. The use of concentrated KOH in the cathode helps to reduce voltage penalty. However, it shows a detrimental effect on the CSE due to the uphill difference in K⁺ concentration between the two chambers, compared to deionized water. Experimental results show energy consumption in the range of 250–500 kJ/mol-CO₂ as a lower range of energy penalty for the regenerator, with CO₂ purity more than 70 percent for a DAC process.

中文翻译：

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电化学从钾盐中剥离 CO2，以便于直接捕获空气


本工作提出了一种电化学再生器用于从碳酸钾/碳酸氢盐流中剥离 CO ₂ 和回收氢氧化钾的实验研究。该再生器适用于水性直接空气捕获 （DAC） 工艺的再生步骤，在该过程中，使用氢氧化钾从空气中捕获 CO ₂ 。在设计有泡沫镍电极的近零间隙电池中进行实验测试，以显示 CO 从含碳流中 ₂ 剥离，研究电流、流速和阳极和阴极盐浓度对电化学再生器性能的影响CO汽 ₂ 提效率 （CSE） 和能耗 （EC）。测试结果表明，在此过程中，以 0.15 M 碳酸钾和 0.15 M 碳酸氢钾的混合物作为钾因子 $k_f,$ ∼1 的进料流，可以实现约 90% 的 CSE，因此降低碱碳比可以进一步提高 CSE 在相同的电流密度下。研究表明，增加钾因子有利于 CSE，而增加缓冲因子对 CSE 有负面影响。此外，对于低于“缓冲阈值”的钾因子，CSE 可以忽略不计。结果还表明，在恒定的钾因子下，对于变化的施加电流，CSE 是恒定的。此外，还研究了再生器阴极室中的支撑电解质 （SEL） 对 CSE 和电压损失的影响。在阴极中使用浓 KOH 有助于减少电压损失。 然而，与去离子水相比，由于两个腔室之间 K ⁺ 浓度的上坡差异，它对 CSE 显示出不利影响。实验结果表明，250–500 kJ/mol-CO 范围内的能耗 ₂ 是再生器能量损失的较低范围，DAC 工艺的 CO ₂ 纯度超过 70%。