Separation of CO₂ from Flue Gas: A Review

Abstract:

As a result of human activity, approximately 7 Gt of carbon are emitted to the earth’s atmosphere each year. A large portion of this carbon is in the form of gaseous CO₂, and approximately 30% of this CO₂ comes from fossil fuel power plants. In addition to rising levels of atmospheric CO₂, the earth’s temperature is increasing. Since CO₂ can act as a trap for heat (similar to the glass in a greenhouse), reduction of CO₂ emissions is an important area of research. Separation and sequestration of CO₂ are near-term goals for emissions reduction. Better fuel efficiency (in power production, transportation, and other areas) can be considered a mid-term goal. An acceptable long-term goal for reducing emissions is using alternate power sources such as nuclear, solar, and wind power. Because separation and sequestration are short-term goals, they are critical and challenging steps for researchers. Methods that are reviewed in this paper include absorption using solvents or solid sorbents, pressure- and temperature-swing adsorption using various solid sorbents, cryogenic distillation, membranes, and several novel and emerging technologies. Upon completion of this review, it was concluded that the most promising current method for CO₂ separation is liquid absorption using monoethanolamine (MEA). While this method is currently most promising, the development of ceramic and metallic membranes for membrane diffusion should produce membranes significantly more efficient at separation than liquid absorption. The other methods investigated in this report are either too new for comparison or appear unlikely to experience significant changes to make them desirable for implementation.