Effects of piperazine on carbon dioxide removal from natural gas using aqueous methyl diethanol amine

CO2 removal process by Amine absorption can be improved by adding an activator such as piperazine (a secondary amine) to the aqueous Methyl Diethanol Amine (MDEA) solution. The shuttle mechanism and the effect of Piperazine on CO2 removal process have been studied and simulated through licensed simulation software, Unisim. The simulation was used to simulate amine absorption process for CO2 removal and to study the effect of the process variables on CO2 removal efficiency. An actual Process Flow Diagram (PFD) was built to simulate the absorption process based on an actual feed gas stream from Egyptian natural gas plant raw gas. The natural gas stream contained 10% CO2 and is treated to reduce the CO2 content to less than 1% by mole. CO2 removal efficiency was investigated by changing process parameters, namely absorption process pressure and temperature, amine concentration and lean amine circulation rate. Piperazine addition, either on account of water or MDEA, increases the absorption efficiency but to a certain limit, when the reaction is no longer mass transfer limited. Temperature decrease improves absorption efficiency, unlike the common behavior of pure aqueous MDEA. Also, decreasing column pressure contributes in reducing CO2 partial pressure in the feed gas and consequently decreases reaction rate with amine. Increasing circulation rate was found to increase the absorption efficiency till reaching the equilibrium.