Effects of carbon treating on piperazine oxidation in pilot plant testing of PZAS™

Abstract

From February to June 2019, a pilot plant campaign was run for 2100 h at the National Carbon Capture Center (NCCC) using moderately degraded 5 m PZ with simulated flue gas equivalent to a 0.64 MW natural gas combined cycle. Piperazine with the Advanced Stripper™ (PZAS™) and a baghouse were used, and N2 sparging was applied at the bottom of the absorber. A carbon bed was activated and showed beneficial effects in removing degradation products and reducing the oxidation rate.The cumulative NH3 production was 180 mmol/k, indicating a PZ oxidation rate of 0.07 mmol/kg/h (0.3 kg PZ/tonne of CO2). The total formate before turning on the carbon bed was 41 mmol/kg, and the total Fe was 0.1 mmol/kg. Carbon treating reduced NH3 production from 0.1 mmol/kg/h to 0.056 mmol/kg/h after 400 h of operation, reduced the UV-Vis absorbance of the samples at 320 nm, and caused a decrease of dissolved Cr. Bench-scale experiments were performed using the NCCC solvent and the same type of carbon. In bench-scale experiments, the UV-Vis absorbance and the concentration of Fe, Mn, and Cr all decreased. A linear equilibrium relationship was observed between the UV-Vis absorbance and the carbon loading.