Characteristics of oxygen mass transfer in a pneumatic mass exchanger for solid-phase oxygen control in the lead bismuth

Abstract

Oxygen concentration in lead–bismuth alloy (LBE) systems has a significant effect on the corrosion rate of structural materials. The corrosion of structural materials by LBE can be effectively mitigated by dynamically adjusting the dissolved oxygen concentration in liquid lead–bismuth. Solid-phase oxygen control technology comprised of a packed bed of lead oxide spheres is widely recognized as an effect and promising solution to regulate the dissolved oxygen concentration, in which how to quantitatively regulate the supplemental solid-phase PbO oxygen source is the key to solid-phase oxygen control technology. This paper innovatively designs a pneumatic mass exchanger for controllable oxygenation without moving parts, and experimentally investigates the oxygen mass transfer characteristics under different temperatures, relative flow velocities, and surface areas of oxygen source areas. By combining an empirical oxygen mass transfer model and the oxygen mass conservation equation, a theoretical prediction model for the reciprocating pneumatic mass exchanger is developed. The results indicate that temperature can rapidly adjust the oxygen dissolution rate, while the relative flow velocity can be used as an effective measure to precisely control the oxygen concentration. The oxygen dissolution rate is directly proportional to the oxygen source surface area. The average relative error of the oxygen concentration between the theoretical prediction model and experimental results is 1.65, with the deviation primarily attributed to discrepancies in oxygen diffusion and the fitting of the mass transfer empirical model. The oxygen concentration in lead–bismuth can be controlled within a reasonable range, thereby validating the oxygenation performance of the novel solid-state oxygen control device—the pneumatic mass exchanger.