According to Aspen HYSYS' user manual, which is accessible via the software itself, the recycle tool is a theoretical block that iterates until a certain threshold is fulfilled. A sufficiently high precision has been achieved by setting the number of maximal allowed iterations to 5000, changing the composition sensitivity from 10 to 1 × 10 -5 and all component sensitivities to 1 × 10 -8 . The error of the smallest molar flow rate before and after the recycle tool is less than 1 × 10 -6 kmol d -1 (compare 𝑛̇C O 2 in streams 11 and 14 in Table in the SI).