Energy Conservation Study in MDEA-Based C02 Removal System

Carbon dioxide (CO2) removal section in Ammonia Plant is highly energy intensive.
Many developments have been made to make it more energy efficient and
environmentally friendly. Absorption of carbon dioxide in an amine based solution
followed by desorption is one of the best available processes to meet the specific plant
conditions of high carbon dioxide purity, minimum hydrogen loss, less corrosion, low
energy requirement and low capital investment. A simplified carbon dioxide removal
system using methydiethanolainine (MDEA) solution have been simulated with the
Aspen HYSYS process simulation tool. Analysis on the operating parameters such as
the absorption temperature and pressure, and also the concentration of MDEA in lean
amine solution have been performed to observe the effect of operating parameters
changes on the absorption rate of carbon dioxide, reboiler duty and C02 ventilation rate.
The comparative study on the structural changes of the absorption system also is being
done to observe the energy performance of the system which apparently can reduce the
capital investment if optimization of the energy requirement can be accomplished.
Based on the base case simulation, 8278.8 kg/hr of CO2 has successfully being removed
from the system with energy requirement of 10.7 MW. Increasing the temperature and
pressure of the lean amine stream has decreased the CO2 absorption rate, C02 removal
rate and reboiler duty. In contrast, raising the concentration ofMDEA in the lean amine
solution has caused the declining of CO2 absorption rate, C02 removal rate and energy
requirement of the reboiler. Subsequently, new configurations of the CO2 removal
system including usage of hydraulic turbine do not contribute in reducing energy
requirement ofthe system. Hence, the energy cost could not be reduced much.