(529a) Structural & Energy Considerations in the Design of Carbon Capture Units

It is well known that the CO2 stripping column is energy intensive and, in power plant applications, can consume ~30% of the energy produced by the power plant. Amine-based absorption-stripping processes represent a well understood carbon capture technology that can be readily deployed and/or retrofitted to meet the need of greenhouse gas reductions from power plants and other industrial manufacturing operations. Conventional absorber-stripper processing units consist of interconnected absorption and CO2 stripping columns as well as various heat exchangers for re-boiling, condensing and exchanging heat between process streams. Standard process designs consist of a single interconnection that feeds CO2-rich solvent to the stripping column and recycles CO2-lean solvent to the absorber.

In this work, we study monoethanolamine (MEA)-based absorption-stripping processes under various lean loadings. The novel aspects of this work include 1) Data-driven vapor-liquid equilibrium. 2) Structural optimizations with multiple recycle streams. 3) The shortest stripping line approach to determine minimum energy designs.

We use experimental data directly to capture and describe the vapor-liquid phase and chemical equilibrium in CO2-MEA-water mixtures. This avoids the need to choose models and fit model parameters to data and provides the flexibility of using laboratory, pilot plant or operation data in modeling and simulation. We also investigate the structural optimization of the absorber coupled to a three-product stripping column with multiple recycle streams. Here both lean (bottoms) and intermediate (side-stream) CO2-loaded solvent streams are recycled back to the absorption column with the purpose of understanding trade-offs between capital investment and energy costs. The shortest stripping line distance approach of Lucia et al. (2008) and iterative refinement (Lucia & Hassan, 2010) are used to find minimum energy requirements and determine if the resulting designs are pinched or non-pinched. Many numerical examples and geometric illustrations are presented and are validated and compared to results using the Aspen Plus simulator with the KEMEA model of Rochelle (2003).