A Three-Stage Process of CO-Selective Methanation Based on Its Reaction Characteristics: Achieving a High Gas Hourly Space Velocity

CO-selective methanation (CO-SMET) is an important technology for CO deep removal from reforming hydrogen. We previously proposed a three-stage CO-SMET with a decreasing temperature profile based on critical CO concentration. In this study, focusing on the sharp decline in each stage’s CO inlet concentration, we further proposed and validated a three-stage CO-SMET process characterized by an increasing space velocity profile, combined with a decreasing temperature profile. Compared to operating all stages at an identical space velocity of 9000 h−1, increasing the space velocities of the second and third stages to 27,000 h−1—thereby raising the overall space velocity from 3000 h−1 to 5400 h−1—only modestly increased the CO outlet concentration from 2.1 ppm to 6.5 ppm, while slightly improving the CO selectivity from 75.3% to 76.3%. These findings offer valuable insights into CO-SMET design that simultaneously achieve high CO-removal depth, high CO selectivity, and high space velocity.