Application of Intercooling to the CO2 Removal Section of an Italian Waste-To-Energy Plant

Carbon Capture, Utilization, and Storage (CCUS), which consists of capturing the CO2 from several emission sources at large-scale, such as power plants and industrial facilities, and storing it underground to prevent it from entering the atmosphere again or utilizing it, is recognized as one of the main technologies for reducing the emissions of carbon dioxide to the atmosphere and to reduce, therefore, the global warming and its detrimental effect on the environment. The application of CCUS has been widely studied for power plants fed with fossil fuels, as coal or natural gas. Only in the past few years has the interest in the possible application to Waste-to-Energy plants risen, also considering that if the origin of the incinerated waste is biogenic, negative CO2 emissions can be obtained by removing it from the flue gas. This paper studies the application of the in-out intercooling and of the pump-around intercooling to the absorption column of a pilot plant for the CO2 removal to be built at the Waste-to-Energy plant at Como, the first one in Italy, in a collaboration among A2A S.p.A., Acinque Ambiente S.r.l., and GASP of Politecnico di Milano. The two options of intercooling have been compared and analyzed in detail to determine the possible advantages in terms of energy savings, by performing sensitivity analyses related to the height of the intercooling in the absorption column, the amount of the liquid flow rate to be withdrawn from the column and cooled before being fed back to the column, the intercooling temperature and finally the lean loading. On the basis of the obtained results, the best configuration for the in-out intercooling is obtained by operating with a withdrawal of 99% of the downflowing liquid flow rate at 15% of the absorber’s packing height. For the pump-around intercooling, the best performance of the unit occurs at 17.5% of the absorber’s packing height with a circulating flow rate three times larger than the lean amine flow rate fed at the top of the absorber. The intercooling temperature is 25 °C for the in-out intercooling and 30 °C for the pump-around intercooling. The lean loading is equal to 0.19 for both the options.