Heat of absorption of CO2 in aqueous ammonia and ammonium carbonate/carbamate solutions

Abstract A reaction calorimeter was used to determine the enthalpies of absorption of CO2 in aqueous ammonia and in aqueous solutions of ammonium carbonate at temperatures of 35–80 °C. The heat of absorption of CO2 with 2.5 wt% aqueous ammonia solution was found to be about 70 kJ/mol CO2, which is lower than that with MEA (around 85 kJ/mol) at 35 and 40 °C. The value decreases with increased loading, but not to as low a value as expected by the carbonate–bicarbonate reaction (26.88 kJ/mol). The enthalpy of absorption of CO2 in aqueous ammonia at 60 and 80 °C decreases with loadings at first, then increases between 0.2 mol CO2/mol NH3 and 0.6 mol CO2/mol NH3, and then decreases again. The behavior of the heat of absorption of CO2 in 10 wt% ammonium carbonate solution was found to be the same as that of aqueous ammonia at loadings above 0.6 mol CO2/mol NH3. The heat of absorption increases with increasing temperature. The heats of absorption are directly related to the extent of the various reactions with CO2 and can be assessed from the species variation in the liquid phase.

[1]  Jared P. Ciferno,et al.  An Economic Scoping Study for CO 2 Capture Using Aqueous Ammonia , 2005 .

[2]  Satish Reddy,et al.  Quantitative evaluation of the chilled-ammonia process for CO2 capture using thermodynamic analysis and process simulation ☆ , 2010 .

[3]  A. E. Sherwood,et al.  The heat of solution of gases at high pressure , 1962 .

[4]  Kaj Thomsen,et al.  Chilled ammonia process for CO2 capture , 2009 .

[5]  Inna Kim.  Heat of reaction and VLE of post combustion CO2 absorbents , 2009 .

[6]  Henry W. Pennline,et al.  Semi-batch absorption and regeneration studies for CO2 capture by aqueous ammonia , 2005 .

[7]  M. Peruzzini,et al.  CO2 absorption by aqueous NH3 solutions: speciation of ammonium carbamate, bicarbonate and carbonate by a 13C NMR study , 2006 .

[8]  B. Poling,et al.  Ion concentrations in the CO2-NH3-H2O system from 13C NMR spectroscopy , 1998 .

[9]  Chang Hyun Ko,et al.  Characteristics of CO2 Absorption into Aqueous Ammonia , 2008 .

[10]  Boshu He,et al.  Experimental study on capturing CO2 greenhouse gas by ammonia scrubbing , 2004 .

[11]  M. H. Brooker,et al.  Ammonium Carbonate, Ammonium Bicarbonate, and Ammonium Carbamate Equilibria: A Raman Study. , 1995 .

[12]  Lawrence B. Evans,et al.  Extension and application of the pitzer equation for vapor‐liquid equilibrium of aqueous electrolyte systems with molecular solutes , 1979 .

[13]  Hallvard F. Svendsen,et al.  Heat of Absorption of Carbon Dioxide (CO2) in Monoethanolamine (MEA) and 2-(Aminoethyl)ethanolamine (AEEA) Solutions , 2007 .

[14]  G. Maurer,et al.  Vapor—liquid equilibria in aqueous solutions of ammonia and carbon dioxide at temperatures between 333 and 393 K and pressures up to 7 MPa , 1988 .

[15]  Hsunling Bai,et al.  Comparison of ammonia and monoethanolamine solvents to reduce CO2 greenhouse gas emissions , 1999 .