The solubility measurement and modeling of CO2 in aqueous solution of N-methyldiethanolaminen+ 2-amino-2-methyl-1-propanol + piperazine at high pressures

• A static equilibrium cell is used for measurement of CO2 solubility in alkanolamine blends at high pressure.
• The vapor–liquid equilibrium of CO2 in aqueous MDEA + AMP + piperazine (PZ) are investigated.
• Increasing the PZ/AMP mass ratio leading to enhancing CO2 acid gas loading.
• Electrolyte NRTL model is successful for modeling of CO2 solubility in binary and ternary blends.

The selective or bulk removal of carbon dioxide from process gas streams is an important step in several industrial processes such as CO2 capturing and sweetening of natural gas. The blend of alkanolamines and a chemical activator such as piperazine (PZ) have been widely used in removal and absorption of carbon dioxide from sour and flue gases. Moreover, an optimal design of an absorber and a stripper needs a detailed knowledge of thermodynamic equilibrium of the acid gas-alkanolamine system. At this work, a new set of experimental data of the solubility of CO2 in aqueous N-methyldiethanolamine (MDEA), 2-amino-2-methyl-1-propanol (AMP) and piperazine (PZ) is presented, keeping the total amine mass percent in the solution at 40, 45 and 50. Using a static equilibrium high pressure cell, the solubility of carbon dioxide in the aqueous MDEA + AMP + PZ system with different mass percent are measured. The results of CO2 partial pressure versus the acid gas loading are obtained at 313, 328 and 343 K and pressure range of 1–40 bars. The CO2 equilibrium absorption enhances by rising pressure, when mass ratio of PZ to AMP in solution varies from 0 to 2. The presence of PZ in the alkanolamine solution leads to intensify the variation of the CO2 partial pressure against its loading. Finally by enhancing temperature, the CO2 absorption reduces in the present alkanolamine mixtures considerably.