I have a scenario which requires a certain percentage of solvent but the problem is of solvent accumulation have added a purge stream but seems like the problem is persisting how do I specify design spec in ASPEN PLus to prevent solvent accumulation.
yes I have a make up stream and the reactants and solvent are mixed inside the reactor due to nature of reaction, will adding a mixer before the reactor help me to slove this problem
You can specify the design spec using specific components (If I got you right) that are accumulating in your system. That is specifying the spec in such a way that only a certain amount of the material is retained in your system based on all the inputs and outputs. Alternatively, I would suggest you use a balance block instead which you can find under flowsheeting option same place you create design spec. I have often used balance block myself and I find them convenient for systems involving recycle. You can create the balance block around the component where you have this problem. Hope this helps.
Thank you for your answer. Can a balance block work with a another constraint of solvent to product ratio which is also required in flash separation to ensure optimal recovery of catalyst from the product?
The design spec on the mixer is a good way to represent the real operation. Imagine that the design spec works like a control loop on the make up stream in order to maintain the total quantity of solvent entering to the reactor. You have to take into account the bounds that you define in the independent variable to achieve convergence under different conditions. It is important also to think about a possible downstream separation. If you have it, you can also a design spec in the separation block to improve convergence.
Thank you for you answer, the solvent will also have an impact on the downstream separation process in this case its a three phase flash which requires a certain mass fraction of solvent to accomplish the separation required. I have figured a certain mole flow rate from design spec which gives me close to convergence results but the moment I specify this flow rate it becomes unsteady again
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