CO2 capture by alkanolamine solutions containing diethylenetriamine and piperazine in a rotating packed bed

Abstract

Aqueous solutions with 30wt% concentration of either diethylenetriamine (DETA) or monoethanolamine (MEA) mixed with piperazine (PZ) were used to capture carbon dioxide (CO2) from a nitrogen gas stream containing 10% of CO2 in a rotating packed bed (RPB). The CO2 capture efficiency of DETA was found to be superior to that of MEA. The mixture DETA+PZ exhibited higher CO2 capture efficiency than DETA itself. This observation indicated the excellent role of PZ for CO2 capture. The effects of temperature, gas flow rate, liquid flow rate, rotating speed, PZ content in solution and oxygen scavenger Na2SO3 content in solution on CO2 capture efficiency and dissolved oxygen (DO) in solution were studied by the 25 factorial design technique. Gas flow rate was found to be the most significant factor affecting CO2 capture efficiency in terms of overall mass transfer coefficient (KGa) and height of transfer unit (HTU), whereas Na2SO3 content in solution was the most significant factor affecting DO. The amount of DO was affected by CO2, more CO2 in solution impeded absorption of O2. A high temperature operation was suggested because CO2 and O2 absorption are chemical and physical absorption processes, respectively. An algebraic model consisted of stirred tanks in series followed by a gas–liquid contactor was proposed to simulate CO2 capture in the RPB. The calculated results with 6-tank in series showed fairly agreement with the experimental data on the exit CO2 concentrations.