Travail de fin d'études et stage[BR]- Travail de fin d'études : Modelisation and optimisation of a CO2 capture process with a new benchmark solvent for the Sart-Tilman cogeneration plant[BR]- Stage d'insertion professionnelle

Abstract

Reducing $CO_2$ emissions which are responsible for global warming is one of the biggest challenge facing humanity. One very promising way to reduce $CO_2$ emissions is a process called Carbon Capture, Utilisation and Storage (CCUS).\\

The method used in this work to capture the $CO_2$ is post-combustion with amines as solvent. This technology suffers from a big drawback which is the high energy requirement for the regeneration of the solvent. Many studies to find the ideal solvent composition for our application were investigated. The choice of the solvent for this work is a $\pm 40$ wt\% formulation of PZ/AMP in a 1:2 molar ratio (3.0 molar AMP ( 26.74 wt\%) and 1.5 molar PZ ( 12.9 2wt\%)) because this solvent is becoming the new benchmark (IEAGHG report, 2019 \cite{IEAGHG-2019}). Indeed, it has shown big improvements in comparison with the conventional benchmark called MEA.\\

The objective of this work is to validate and optimize a post-combustion $CO_2$ capture model using Aspen Plus V11.0 as software and then, to apply it for the Sart Tilman cogeneration plant. The goal was to treat a realistic fumes composition and mass flow exhausting from the CHP plant with the new benchmark solvent and to consume as little energy as possible.\\

First, the model was built and validated by trying to reproduce some experimental results from the literature. The capture rate, reboiler duty and lean and rich loading were studied to perform the validation. An Absolute Average Relative Deviation of respectively 2.2; 2; 8.7 and 9.1 \% was found between our model and the experimental results which was satisfying.\\

Then, different sensitivity analysis were performed by varying parameters that directly affect the energy requirement of the process using equilibrium mode for the calculations in the columns. Optimized parameters are the following: 14 and 8 stages were found for the absorber and the stripper respectively; a solvent mass flow rate of 70000 kg/h was determined; the heat-exchanger temperature approach was fixed to 5\degree C and the stripper pressure could be increased to 2.3 bar. \\ The rate-based mode, taking into account heat and mass transfer limitations in the columns was used in a second step to determine the sizing of the 2 columns: 7 and 4 m for the total heights of the absorber and the stripper were found and the diameters are respectively 2.1 and 1.2 m.\\ \\ Finally a comparison between the 2 types of calculation mode in the columns (equilibrium and rate-based) was done. A small decrease was got for the reboiler duty from 3.58 GJ/$t_{CO_2}$ for the equilibrium mode to 3.49 GJ/$t_{CO_2}$ for the rate-based mode due to a higher lean loading and a higher stripper pressure allowed without solvent degradation.