Influence of MEA and piperazine additives on the desulfurization ability of MDEA aqueous for natural gas purification

The influence of monoethanolamine (MEA) and piperazine added into methyldiethanolamine (MDEA) aqueous solution on the desulfurization of natural gas was investigated by the method of equilibrium data determination in this paper. Four kinds of equilibrated systems, i.e. H2S-NG-MEA-water, H2S-NG-MDEA-water, H2S-NG-(MEA-MDEA)-water, H2S- NG-(MEA-MDEA-PZ)-water at the temperature ranging from 298.15 to 333.15 K were measured in a glass-jacketed gas absorption cell with a double-drive impeller device. The results show that the H2S partial pressure increases with the increase of H2S loading in liquid phase along an isotherm. The addition of MEA and PZ is beneficial for improving the desulfuration ability of MDEA. The ability of H2S absorption for the four mixed alkanolamine systems is MEA > (MEA-MDEA-PZ) > (MEA-MDEA) > MDEA according to the order of size. The four equilibrium data can be well correlated with the Soave–Redlich–Kwong equation of state and electrolyte-NRTL activity coefficient model. The overall mean relative errors of total pressure and H2S partial pressure between the calculated and experimental data of the four systems are 3.30 and 3.07 %, respectively. The experimental and calculated results are very useful for desulfuration and purification process of natural gas or other industrial gases.