ASPEN cycle

Thread Content

Figure 1 shows a process I designed, in which the feed loop has been connected, but convergence is not achieved when ethanol is connected. In Figure 2, stream 1 is the initial feed, while stream S101 is the recycled stream combined with additional fresh feed (which is an 80% ethanol solution); a calculator is used to ensure that the masses of these two streams are equal. Figure 3 shows the result of one iteration, using the material composition of S101 in Figure 2 as the composition of stream 1; slight differences between the two can be observed. When attempting to replace stream 1 with stream S101 (that is, to connect the ethanol circuits together), an error occurs and the process does not converge. Since a design requirement was added to Tower T106 to ensure a low concentration of heavy components at the top of the tower, an error is reported indicating that this requirement is not met when circulation is enabled; however, if this design requirement is removed, none of the other towers can meet the separation requirements. I’m asking the experts here: how can I make it work so that it can loop? Thank you!