Studies on the effect of addition of piperazine and sulfolane into aqueous solution of N-methyldiethanolamine for CO2 capture and VLE modelling using eNRTL equation

Abstract

In this work, new experimental vapour liquid equilibrium (VLE) data and modelling work of VLE of CO2 in piperazine (PZ) activated aqueous solutions of n-methyldiethylamine (MDEA) are presented. Besides, experimental VLE data of CO2 in a hybrid solvent, containing sulfolane as physical solvent along with aqueous (MDEA+PZ), have also been reported over the temperature range of 308–328K and CO2 partial pressure range of 1–1400kPa. The concentrations of MDEA in the aqueous solutions are 22–28mass% and also 42–48mass%. PZ is used as a rate activator within a concentration range of 2–8mass%. The total amine concentration in the aqueous solutions of (MDEA+PZ) has been kept within 30mass% and also 50mass%, while for the hybrid solvent the concentration of sulfolane has been maintained at 10mass% along with total 50mass% (MDEA+PZ). Electrolyte non random-two liquid (eNRTL) theory has been used to model the VLE. It has been found that there is a good agreement between the experimental and model results of CO2 solubility in PZ activated MDEA solutions. The CO2 cycle capacity is calculated considering a set of lower and higher CO2 partial pressures corresponding to lower (lean solvent) and higher (rich solvent) equilibrium CO2 loadings. For the sulfolane based hybrid solvent, it has been observed that the CO2 cyclic capacity of the solvent decreases with the lower lean-rich partial pressure range of 10–100kPa, but increases at higher partial pressure ranges of 100–1000kPa at 323K. PZ mass% in the hybrid solvent has also been found to have a positive effect on the CO2 cyclic capacity.