Aqueous piperazine as the new standard for CO 2 capture technology

Abstract

Amine scrubbing will be the technology of choice for CO 2 capture from coal-fired power plants. 7 m monoethanolamine (30 wt% MEA) has been the standard solvent to represent the capability of this technology. This paper presents a new standard process that uses 8 m piperazine (40 wt% PZ) with regeneration at 150 °C by a two-stage flash. The performance data for the piperazine system is non-proprietary and available for standard comparisons. The expected energy requirement for a piperazine or other advanced amine scrubbing processes will approach 220 kWh/tonnes CO 2 removed. The minimum work for this separation is 113 kWh/tonnes. The major exergy losses (kWh/tonnes CO 2) in the piperazine process are: condenser, 34; exchanger, 25; compressor, 22; absorber, 14. Because mechanical adiabatic compression has an overall thermodynamic efficiency of 55–60%, amine scrubbing with thermal swing regeneration provides better energy performance with greater heat of CO 2 absorption and maximum regeneration temperature. Piperazine can be used up to 150 °C without significant thermal degradation. This allows better energy performance and minimizes the impacts of degradation products. The piperazine solvent is resistant to oxidative degradation, has less volatility than MEA, and is not corrosive to stainless steel. It is also suitable for reclaiming by distillation and other methods already commercialized by the gas treating industry.