A process of CO 2 removal from a flue gas comprising: (a) contacting in an absorber a flue gas comprising CO 2 with a CO 2 lean ammonia-comprising medium and/or regenerated CO 2 lean ammonia-comprising medium having an ammonia concentration, to absorb CO 2 from said flue gas into said CO 2 lean ammonia-comprising medium and/or regenerated CO 2 lean ammonia-comprising medium to produce a CO 2 rich ammonia-comprising medium; (b) heating the CO 2 rich ammonia-comprising medium, using a heating medium, to release CO 2 from said CO 2 rich ammonia-comprising medium to produce a regenerated CO 2 lean ammonia-comprising medium, the heating taking place at an operating pressure in a regeneration vessel having a sump; (c) supplying the regenerated CO 2 lean ammonia-comprising medium to said absorber; (d) identifying a desired mole ratio of ammonia to CO 2 of the CO 2 lean ammonia-comprising medium and/or regenerated CO 2 lean ammonia-comprising medium brought into contact with the flue gas to control a CO 2 capture rate of said absorber and/or to control ammonia emissions from said absorber; (e) predicting a desired temperature of regenerated CO 2 lean ammonia-comprising medium present in the sump of the regeneration vessel by means of the ammonia concentration of the CO 2 lean ammonia-comprising medium and/or regenerated CO 2 lean ammonia-comprising medium, the operating pressure of the regeneration vessel and the identified desired mole ratio; (f) controlling the temperature of regenerated CO 2 lean ammonia-comprising medium present in the sump of the regeneration vessel based on the predicted desired temperature; and (g) using a control unit to adjust a regulating valve, arranged to control a flow of the heating medium, based on a signal of a NH 3 concentration indictor representing the NH 3 concentration of flue gas leaving the CO 2 absorber. (a) contacting in an absorber a flue gas comprising CO 2 with a CO 2 lean ammonia-comprising medium and/or regenerated CO 2 lean ammonia-comprising medium having an ammonia concentration, to absorb CO 2 from said flue gas into said CO 2 lean ammonia-comprising medium and/or regenerated CO 2 lean ammonia-comprising medium to produce a CO 2 rich ammonia-comprising medium; (b) heating the CO 2 rich ammonia-comprising medium, using a heating medium, to release CO 2 from said CO 2 rich ammonia-comprising medium to produce a regenerated CO 2 lean ammonia-comprising medium, the heating taking place at an operating pressure in a regeneration vessel having a sump; (c) supplying the regenerated CO 2 lean ammonia-comprising medium to said absorber; (d) identifying a desired mole ratio of ammonia to CO 2 of the CO 2 lean ammonia-comprising medium and/or regenerated CO 2 lean ammonia-comprising medium brought into contact with the flue gas to control a CO 2 capture rate of said absorber and/or to control ammonia emissions from said absorber; (e) predicting a desired temperature of regenerated CO 2 lean ammonia-comprising medium present in the sump of the regeneration vessel by means of the ammonia concentration of the CO 2 lean ammonia-comprising medium and/or regenerated CO 2 lean ammonia-comprising medium, the operating pressure of the regeneration vessel and the identified desired mole ratio; (f) controlling the temperature of regenerated CO 2 lean ammonia-comprising medium present in the sump of the regeneration vessel based on the predicted desired temperature; and (g) using a control unit to adjust a regulating valve, arranged to control a flow of the heating medium, based on a signal of a NH 3 concentration indictor representing the NH 3 concentration of flue gas leaving the CO 2 absorber.