Review of Recent Pilot Plant Activities with Concentrated Piperazine

Abstract

Concentrated 5 molal (m) piperazine (30 wt% PZ) is a novel solvent being developed by the University of Texas at Austin for CO2 capture from coal-fired power plants. In March 2015, a campaign at the UT Austin Separation Research Program (SRP) pilot plant evaluated the advanced flash stripper configuration with 5 and 8 m PZ. The absorber was operated with two gas rates: 350 and 500 acfm. The liquid to gas ratio (L/G) was varied from 2.3 to 5.0 lb/lb. The in-and-out and pump around spray recycle intercooling were operated at 40°C. Seventeen runs were operated with 5 m PZ and four runs were completed with 8 m PZ. The lean solvent CO2 concentration was varied from 0.18 to 0.26mol CO2/mol PZ equivalent. The CO2 removal rate in the absorber was varied from 69 to 97%. The advanced flash stripper was operated at temperatures and pressures that varied from 135 to 149°C and 4.2 to 7bar, respectively. The cold rich bypass was varied from 0 to 13% and the warm rich bypass was varied from 17 to 41%. 5 m PZ gives 20% better heat transfer performance than 8 m PZ on the LP cross exchanger and resulted in a lower process heat duty because of lower viscosity. Seventeen runs with optimized rich solvent bypass rates achieved process heat duties from 2.1–2.5 GJ/tonne CO2. This campaign demonstrated that using the advanced flash stripper reduced the energy requirement by 25% compared to the previous two SRP campaigns with the two-stage flash configuration.