Correctness of ASPEN software simulation results
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When I used ASPEN to simulate the absorption stabilization system (four towers), I had two comparison cases.: The feed materials are exactly the same, quality, composition, etc. ； Then there are four material streams exported from the absorption and stabilization system, including light diesel oil, liquefied gas, dry gas and stabilized gasoline. Both cases converge. However, after I added up the four export logistics mass flows, I found that the export logistics mass flows of the two cases were not equal, and the results were very different, which reflected that the materials in the entire system were not conserved. Please tell me how to solve this situation? ? ?
1. Carefully check whether the materials in the two cases are mass conserved. If not, the ASPEN software has an error.； 2 If 1 is conserved, the material balance boundary is inconsistent.: For example, partial stable gasoline circulation, some non-condensable gas at the top of the stable tower, and partial water cutting are not considered.
If it is the recovery rate of the tower, it can be considered to be set, and it should not be different.
I have carefully calculated and considered the above situations, and this problem does exist.: The feed is 87900kg/h, but the discharge is 87889kg/h. There is a gap of 11kg/h. The gap of 11kg/h is not allowed in this simulation. What I mean is that because the software itself converges iteratively, the gap in components is determined by the convergence conditions. How do we reduce this gap in simulation? ? Can a true material balance be achieved? ? It is easy to achieve material balance in one tower, but it is difficult to achieve it when there are several towers and there is circulation of material streams? ? The overall feeling is that this gap is caused by the accumulation of errors! This post was last edited by newlgt on 2009-4-16 13:00 ]
11/87900=0.0001 has reached an accuracy of one ten thousandth, which is allowed in engineering. If you want to continue to reduce it, you need to increase the simulation convergence accuracy in convergence/Conv Options. Change it from 0.0001 to a smaller value. However, it is difficult to converge and you need to increase the number of iterations.
If the initial value is set to the result of your current simulation and the convergence accuracy is improved, it should be quite easy to converge, right?
I think what you said above is more correct, you might as well give it a try
Because you are using a tower handle? This question is very common. It does not mean that your mass is not conserved. In fact, it is. It's not a matter of accuracy either. But there is a water element on the top of some towers, and you lead it out.
It is indeed a problem of convergence accuracy. I wonder if the person above has calculated it?