Natural Gas Sweetening

If natural gas contains appreciable amounts of acid gases, namely, carbon dioxide (CO2) and hydrogen sulphide (H2S) there is a need for the gas to undergo treatment. This step is necessary so as to render natural gas marketable and safe. Several techniques can be used to lower the concentration of acid gases— the most prominent being the amine process. As illustrated below, feed (raw) gas comes in contact with a lean amine solution in the absorber which selectively combines with the acid gases and removes them to a large extent.

Typical acid gas removal amine unit.

The two most common basic chemical solutions utilized in an amine unit refer to MonoEthanolAmine (MEA) and DiEthanolAmine (DEA). Following their regeneration, at an appropriate temperature, amines can expel a portion of the acid gases. Hydrogen sulphide reacts almost instantaneously with the amines by proton transfer, while carbon dioxide (CO2) combines with primary and secondary amines to form a carbamate.

In this research, we examine the reaction kinetics of CO2. Several mechanisms of chemical reactions exist with the General Zwitterion being the most applicable for CO2 since its kinetic overall reaction rate is first order in nature with respect to CO2 and second order with respect to the amine. In this project we investigate some of the pertinent parameters and operating conditions with particular emphasis on improving process performance. Results aim to determine the optimal operating conditions of the amine process at the lowest possible costs. Process simulations are conducted in Aspen Plus and HYSYS and, where deemed necessary analytically modelling complements the study.

Project is partly funded by the Ministry of Energy of the Republic of Cyprus.

Commencement date: Sept. 2017-

Research Team: Ms Yiota Argyrou, Dr Constantinos Hadjistassou

Publications: Coming soon…