Carbon Dioxide Capture by Aqueous Piperazine
Background 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.
Invention Description A new solvent composition has been identified for piperazine to capture CO2 from coal-fired flue gas, hydrogen, or natural gas. When combined with advanced stripper configurations, this solvent produces a large capacity for CO2 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.
Market Potential/Applications 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.
Development Stage Proof of concept
Gary T. Rochelle
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