CO2 Capture by amine absorption

Mono Ethanol Amine (MEA) is a primary amine, widely used at industrial scale for gas separation. There is a great focus towards promoting the solvent to increase the efficiency of the CO2 capture process and decrease the energy consumption on regenerating the solvent.

In this study, we focus on the application of the amine scrubbing process for CO2 capture from industrial gases containing low to a very high mole percentage CO2 (up to 40% CO2), as observed in for example biogas upgrading.

This study aims to investigate the impact of using well-engineered additives to impact the following sections of the capture process:

  1. Reboilers
  2. Wash sections
  3. Cooling sections and heat exchangers
  4. Absorber design

The studied additives posess the characteristics of changing the fluid properties to alter the process features, which can provide optimal process conditions. More specifically, the amine solvents contain a significant amount of water which consume a large amount of energy at the stripper reboiler during evaporization. In order to reduce the reboiler duty, in this study, we take advantage of the designer-additives (VRAs) to reduce the vaporization of water, which in turn reduces the need for reboiling, low-temperature washing, and cooling, and facilitates the heat exchange. 

The goal of this project is to benchmark the MEA process compared to MEA with various VRAs. The benchmarking will be performed using Aspen Plus.

Aspen Plus is used as a basis for process simulation in this study. Three approaches will be used:

  1. Equilibrium based approach
  2. Rate based approach
  3. CAPCO2 (DTU rate based model)

DTU has its own in-house rate-based simulation engine called CAPCO2 which is applicable in Aspen Plus as a user model through the Aspen Customer Model interface. It is a very complex set of first-principles partial differential equations which are solved by discretization through the column height. These can predict the mass transfers by having only the most basic information of column size and solvent kinetics. The information on second-order reaction kinetics is measured by for example a wetted wall column.

The energy consumption is the most serious issue in CO2 capture by amine scrubbing. In this study, the operational parameters are optimized to find the lowest energy consumption by optimization. Studied parameters are lean CO2 loading, lean temperature, inner diameter, column heights, and absorption/desorption pressure.

From this comparison, the pros and cons of VRAs in MEA aqueous solutions for CO2 capture processes will be shown, and their specific changes in key performance measurements such as CO2 removal percentage, temperature, and CO2 concentration profile in absorber, heat exchange, wash section, and desorber energy consumption will be explained.

Main supervisor: Philip Loldrup Fosbol

 


Contact

Amirali Rezazadeh
PhD student
DTU Chemical Engineering

Contact

Philip Loldrup Fosbøl
Associate Professor
DTU Chemical Engineering
+4545 25 28 68