NAVAL RESEARCH LAB WASHINGTON DC WASHINGTON United States
A sea-based synthetic fuel process that combines carbon dioxide CO2 and hydrogen H2 to make jet fuel at sea is envisioned. However, before such a process can become feasible, methods must be developed to extract large quantities of CO2 and H2 from seawater fast and efficiently. An Electrolytic Cation Exchange Module E-CEM has been developed and extensively evaluated at a seawater flowrate of 0.5 gallons per minutegpm as a function of pH, current density, time, polarity reversal, and CO2 and H2 recovery. These evaluations have established E-CEM design parameters that are currently being used to scale-up and construct an E-CEM prototype capable of processing up to 25 gpm of seawater. This fifty time scale-up has led to the need to regulate E-CEM effluent discharge water composition with respect to pH and chlorine content. This report details the results of two separate evaluations of the E-CEM that specifically address changes in E-CEM performance and effluent concentrations with changes in influent electrode water composition and flowrate. These evaluations have identified additional software and hardware capabilities that will be included in in the prototype skid to ensure E-CEM performance and operational safety while maintaining effluent water quality.