Material is not conserved in the cyclic process

It seems impossible. Could you be more specific?

It’s a process that involves reaction followed by separation; the unreacted raw materials separated in several separation columns are recycled back to the reaction tank. However, after this recycling, the material balance in the two subsequent columns is not maintained, and I don’t know how to adjust it. It is caused by this circulating flow.

The circulating flow can be interrupted first; the process is adjusted so that the levels on both sides of the circulating flow become similar, and then the circulation is resumed

Your problem is mainly caused by non-convergent calculations; the more circular flows there are, the harder it is to achieve convergence, which is reflected in the lack of conservation of mass and energy in your simulation report. The main reasons are as follows: First, your initial values are not appropriate – that is, the temperature, pressure, and composition of the feed material, as well as the requirements for the separated products (i.e., the data you enter in the simulation). These are issues related to the initial values. You can first stop the cyclic flow, adjust the process so that the conditions on both sides of the cycle are similar, and then use the calculated results as the initial values before restarting the cyclic flow. The second issue is the choice of your convergence method; Aspen uses the standard convergence method by default, but you need to select an appropriate one depending on the degree of non-ideality of your system under study. For cases with strong non-ideality, the Newton method and the strongly non-ideal method can be tried. Third, you can set your number of iterations to a maximum of 200. The default number of iterations for Aspen is 25.

Increasing the computational precision may lead to slower convergence, but the results will be more accurate