Carbon Dioxide Capture by Aqueous Piperazine
Physical Sciences : Chemical
Available for licensing
- Gary Rochelle, Ph.D. , Chemical Engineering
- Marcus Hilliard , University of Texas at Austin
The conventional process for CO2 absorption/stripping uses aqueous amines such as monoethanolamine (MEA). Piperazine has previously been identified as a very reactive amine. It is an attractive alternative to MEA because it reacts with CO2 thirty times faster than MEA. However, piperazine is a solid at ambient temperature that has a limited soubility in water. Furthermore, the boiling point of liquid piperazine is less than that of MEA, so it is expected to have a greater volatility than MEA. Therefore, aqueous piperazine by itself has not received any known commercial usage in CO2 absorption/stripping, because it is perceived to be too volatile and cannot be used at concentrations that provide high capacity for CO2 absorption.
A new solvent composition has been identified for piperazine to capture CO from coal-fired flue gas, hydrogen, or natural gas. When combined with advanced stripper configurations, this solvent produces a large capacity for CO absorption with very fast rates of absorption at a high heat of absorption. The energy requirement should be reduced by 10 to 30 percent from conventional 30% MEA solvents.
The reactive amine will be three to ten times more expensive than MEA; but, unlike MEA, it will not degrade thermally, nor does it react quickly with oxygen in the presence of dissolved iron.
- Net energy consumption should be reduced by 10 to 30%.
- Piperazine is more stable than MEA, thereby reducing secondary environmental impact and makeup rates.
- Piperazine solutions absorb CO2 20% to 100% faster than MEA.
- Piperazine can be recovered in a thermal reclaimer by evaporation.
As concerns of global climate changes spark initiatives to reduce carbon dioxide emissions, its economic removal from gas streams becomes increasingly important. Removal by absorption/striping is a commercially promising technology, as it is well suited to sequester CO2 from gas streams produced by coal-fired power plants. This process can be expensive, potentially increasing the cost of electricity by 50%; therefore, technology improvements to reduce operating cost, such as the use of the aqueous piperazine described herein, are desirable.
Proof of concept
- 2 foreign patents issued
- 1 U.S. patent issued: 7,938,887