https://doi.org/10.1016/j.seppur.2021.118959
“Aiming at decreasing the energy consumption while meeting environmental limits regarding NH3 emissions, the mild-temperature NH3-based capture process developed by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) proposes to couple the water washing of the CO2-depleted FG with the FG pre-treatment column placed upstream of the CO2 absorber [19]: in addition to cooling down the FG, the NH3-rich stream obtained in the water-wash column removes SO2 from the inlet FG, while the heat contained in the inlet gas should be able to strip-off the NH3 from the solvent; NH3 is recycled to the CO2 absorber within the FG and the regenerated NH3-lean solution, after undergoing chilling, is used to capture NH3 from the CO2-depleted FG exiting the CO2 absorber. Nevertheless, the temperature of the FG at the stack is below ambient [19], which penalizes the dispersion of the gas plume. Subsequently, CSIRO has updated the process by including the removal of NOx from the inlet gas, thus leading to the so-called advanced, NH3-based combined NOx/SOx/CO2 emission control process [20]: firstly, NO is oxidized to NO2 and SO2 is removed from the FG using a NaClO2 aqueous solution; secondly, the NO2 is removed from the FG by means of the NH3-rich solution generated out of the water-wash column that eliminates NH3 from the FG exiting the CO2 absorber; finally, further NH3 removal from the CO2-depleted FG is achieved by means of acid washing using the solution generated out of the SO2 removal and NO oxidation stage. Although the advanced CSIRO’s process allows to reach higher FG temperatures at the stack, i.e. around 50 °C, the thermal energy requirements for the regeneration of the NH3-lean stream are not avoided in this case and depend strongly on the NH3 concentration in the CO2-depleted FG thus on the CO2 absorber operating conditions [21].”