Influence of Gas Injection Pipe on CO₂ Decomposition by CaCl₂–CaO Molten Salt and ZrO₂ Solid Electrolysis

Abstract

The electrochemical decomposition of carbon dioxide to form carbon and oxygen gas in CaCl₂–CaO molten salt was studied. A water model experiment was carried out to study the influence of the tip shape of the pipe, the pipe diameter and the wettability of the gas injection pipe on the bubble shape in the molten salt. Bubbles were formed with both a horizontal tip and an oblique tip when the wettability of the gas injection pipe was good. The specific surface area of the bubbles when using the oblique tip was smaller than when using the horizontal tip. On the other hand, slug flows appeared when wettability was poor. In a hot model experiment, the current density was measured, and it was found that the CO₂ gas concentration decreased. Precipitated carbon was detected from the sample after the experiment. With the same pipe, the decrease of the CO₂ gas concentration when using the oblique tip was more remarkable than when using the horizontal tip. It is likely that the form of the CO₂ gas in the molten salt was bubble-shaped.