Degradation of aqueous DEA solutions in a heat transfer tube

To study the degradation of aqueous diethanolamine (DEA) solutions in heat transfer equipment, DEA solutions were passed through a coiled heat transfer tube (2.032 mm ID, 3.175 mm OD, 4.8 m long) immersed in a constant temperature bath. The operating conditions were: DEA flow rate 0.011 to 0.0172 L/s, DEA concentration 20 to 40 wt%, DEA temperature 60 to 200°C, CO2 partial pressure 1.38 to 4.18 MPa. The degradation rate was found to increase with temperature, DEA concentration and CO2 partial pressure; it decreased slightly with solution flow rate. The degradation was accompanied by the formation of a fouling deposit. A simple mathematical model is presented for predicting DEA degradation.