15th 18th March 2021 Abu Dhabi, UAE Effects of carbon treating on piperazine oxidation in pilot plant testing of PZASTM

Abstract

Aqueous piperazine (PZ) has shown promise as a solvent to reduce CO2 emissions due to its high CO2 absorption rate, capacity, and thermal stability. From February to June 2019, a pilot plant campaign was run for 2100 hours at the National Carbon Capture Center (NCCC) using slightly 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 throughout the campaign, 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/kg over the 2100 hours, indicating a PZ oxidation rate of 0.07 mmol/kg/hr, equivalent to 0.3 kg PZ/tonne of CO2. The final total formate before turning on the carbon bed was 41 mmol/kg, and the total Fe was 0.1 mmol/kg, both lower than other pilot plant results. Both total formate and ethylenediamine (EDA) were found to accumulate faster at lower temperature Carbon treating reduced NH3 production from 0.1 mmol/kg/hr to 0.056 mmol/kg/hr after 400 hrs of operation, reduced the UV-vis absorbance of the samples at 320 nm from 58.3 A to 17.4 A, and caused a decrease of Cr concentration. Bench-scale experiments were performed using the NCCC solvent and the same type of carbon (8*30 mesh, lignite- based granular activated carbon) In bench-scale experiments, the UV-Vis absorbance and the concentration of Fe, Mn, and Cr all decreased. A linear relationship was observed between the equilibrium UV-Vis absorbance and the carbon loading