Which statement about low‑pressure CO2 storage is correct?

• A. 850 psi at 70°F
• B. 300 psi at 0°F
• C. 400 psi at 20°F
• D. 150 psi at -5°F

Answer: (B)

CO2 storage pressure tracks its temperature because CO2 in these systems is kept as a saturated liquid with some vapor above it. The pressure inside the storage vessel equals the saturated vapor pressure of CO2 at the storage temperature. In low‑pressure storage, designers aim for a relatively modest pressure at typical cold temperatures, which is why about 300 psi at 0°F is the standard reference point. As temperature rises, the vapor pressure climbs—so at around 70°F the pressure would be much higher (on the order of several hundred psi to near a thousand), while at very cold temperatures it drops correspondingly (roughly 150 psi at -5°F, about 400 psi near 20°F). Therefore, 300 psi at 0°F reflects the expected low‑pressure storage condition.