A novel application of the SAWD-Sabatier-SPE integrated system for CO ₂ removal and O₂ regeneration in submarine cabins during prolonged voyages

To improve the working and living environment of submarine crews, an integrated system of CO₂ removal and O₂ regeneration was designed to work under experimental conditions for 50 people in a submarine cabin during prolonged voyages. The integrated system comprises a solid amine water desorption (SAWD) unit for CO₂ collection and concentration, a Sabatier reactor for CO₂ reduction and a solid polymer electrolyte (SPE) unit for O₂ regeneration by electrolysis. The performances of the SAWD-Sabatier-SPE integrated system were investigated. The experimental results from the SAWD unit showed that the average CO₂ concentration in the CO₂ storage tank was more than 96% and the outlet CO ₂ concentration was nearly zero in the first 45 min, and less than 1/10 of inlet CO₂ after 60 min when input CO₂ was 0.5% (1000 L). About 950 L of CO₂ was recovered with a recovery rate of 92%∼97%. The output CO₂ concentration was less than 0.2%, which showed that the adsorption-desorption performance of this unit was excellent. In the CO₂ reduction unit we investigated mainly the start-up and reaction performance of the Sabatier reactor. The start-up time of the Sabatier reactor was 6, 8 and 10 min when the start-up temperature was 187.3, 179.5 and 168 °C, respectively. The product water was colorless, transparent, and had a pH of 6.9∼7.5, and an electrical conductivity of 80 μs/cm. The sum of the concentration of metal ions (Ru³⁺, Al³⁺, Pb ²⁺) was 0.028% and that of nonmetal ions (Cl^-, SO ₄ ^2-) was 0.05%. In the O₂ regeneration unit, the O₂ generation rate was 0.48 m³/d and the quantity was 2400 L, sufficient to meet the submariners' basic oxygen demands. These results may be useful as a basis for establishing CO₂-level limits and O ₂ regeneration systems in submarines or similar enclosed compartments during prolonged voyages.