Pilot Plant Results with Piperazine

Abstract

Concentrated (40wt %) piperazine (PZ) with two-stage flash regeneration is an advanced second generation amine-based process for CO2 capture. Two pilot campaigns with the two-stage flash process were completed in 2011 and successfully demonstrated high temperature stripping at 150°C with concentrated piperazine. Data reconciliation for the absorber with intercooling return spray was completed using Aspen Plus® Data-Fit. Data reconciliation for the two-stage flash with warm rich bypass was completed using Aspen Plus® Data-Fit and a dynamic model developed in MATLAB®. The results of data reconciliation analysis found that the CO2 loading in the lean and rich streams needed to be systematically shifted upward, 4.6–4.7% in the stripper analysis and 7.5% in the absorber analysis.An analysis of the October 2011 campaign pilot plant data identified the two configurations with the lowest equivalent work as the high temperature two-stage flash with warm rich bypass and low pressure simple stripper. The calculated equivalent work for the two-stage flash with warm rich bypass from raw pilot plant data and reconciled pilot plant data is approximately 35kJ/mol CO2 and 36.6kJ/mol CO2, respectively. Intercooling with a spray return improved absorber CO2 removal performance by 6–7% at the lower gas rates and was found to be equivalent to a 7– 20% increase in packing height based on reconciled data results. Warm rich bypass to the low pressure flash tank reduced piperazine volatility by factor of two in the condensate. In addition, analysis of the pilot plant piperazine inventory at the end of the campaign identified the following degradation products (mmol/kg): N-formyl PZ (1.3), ethylenediamine (13), aminoethylpiperazine (3.6), Hydroxyethylpiperazine (3.9), formate (1.0), and N-nitroso- piperazine (0.09). The solvent analysis also found that the CO2 capacity has decreased by 17%, with a slight decrease in CO2 absorption rate and heat of vaporization.