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It introduces a number of features that must be understood to complete even a simple simulation. The chapter aims to understand some of the features of Aspen Plus while creating a simulation of the mixture of a feed stream of 100 kg/h of the 50/50 acetone‐water mix with a solvent stream of 100 kg/h of methyl isobutyl ketone (MIBK).
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Your post MUST be submitted as a. I used to work for a company that made a simulation product kind of like Aspen, and was involved in the deployment of it. I have just started using Aspen for my senior design project, and would not consider myself an expert in any way, shape or form.I'm assuming at some point you have had to iteratively solve an equation where you guess at a value, calculate it, and then recalculate based off of your answer. Aspen does this for many of the unit operations that are carried out. When it says that it can't converge, that means that it tried to solve the equation too many times to reach the desired limit of error between the guess and the solution.There are a couple possible reasons why it can't converge.Your limit on the number of iterations may be too low, or your tolerances too tight. You can usually change those inside of the equipment.Your input values are unreasonable for the specified equipment. If the sizing of the equipment isn't appropriate, you may never reach a valid solution.The order of the calculations carried out.
Since you have a recycle stream, you may get a circular loop where one piece of equipment tries to calculate a certain value that some other equipment uses in an equation. Iterations can become a big deal here.I don't know how to fix your problem, but those are some of the things that can happen with simulation software that prevent convergence.
Want to post?STOP. If you don't see what you're looking for, then please post.This subreddit is primarily for practicing Chemical Engineers to discuss topics related to their discipline and the practice of engineering. It is not primarily for coursework or job hunting.For student-related questions, visit.For job hunting and career advice, use our monthly sticky thread or the biweekly sticky thread on.Have a more general question? TryIf your post is not showing up, message the mods. Posts are frequently caught by the spam filter and it may take a few days to notice without contacting one of us.Check out the official Discord for:Active Moderators. Hello everyone,I have finished a flowsheet in aspen plus with a recycle stream and a lot of design specs in it. All seems to be right, but when I simulate it, the simulation ends with numerous errors and warnings.
It says that one block is out of mass balance and one of the solvers doesnt convert in xy iteration steps. However when i choose better initial numbers the solvers do converge and the errors are gone. Does anybody know where to find the setup to adjust for more iteration steps for the solvers? I hope that with more steps convergence will be ensured even with ‘bad‘ initial numbers. So if it doesnt converge e.g.
In 30 steps, maybe it will in 60.did you run into the same problem? How did you solve it and how would you approach it in general?Thanks a lot!!! As far as I know, you have to set it separately for each block. For example, in the Flash Block, you can change the number of iterations in the 'Flash Options' tab. Although, the option isn't in the same spot for each block.Something that I've found useful when running recycle streams is to start out without the recycle hooked up, but have an independent stream that will have about the same parameters as the recycle stream. Run it once and have it converge; this should give the blocks and streams good initial values.
Then disconnect the independent stream and connect the recycle back and it should converge with little issue.