Material Balances: Interactive Simulations

These simulations were prepared using Mathematica. Download the free Wolfram player, and then download the simulation CDF file (link given below or click on figure to download). Try to predict the behavior when a parameter changes before using a slider to change that parameter. Screencasts below explain how to use these simulations.

Mass balances are demonstrated for a reactor system. Pure A is fed to the system and two parallel reactions take place in the reactor: 
          A → B   (desired)           A → C  (undesired)
A separation unit after the reactor removes some of the unreacted A and recycles it back to the feed stream. A slider sets the recycle ratio, which is the ratio of the recycle flow rate to the fresh feed flow rate. The reactor selectivity, which is the (flow rate of B)/(flow rate of C) leaving the reactor, is set with a slider. The reactor conversion, which is the percent of A entering the reactor that is consumed, is also set with a slider. The overall conversion of A is the percent of the feed to the system (100 mol A/h) that is consumed. The yield is the percentage of the feed to the system (100 mol A/h) that is converted to the desired product B. A negative flow rate of A exiting the system indicates the combination of reaction selectivity and reactor conversion is not possible.

Try to answer this question before determining the answer with the simulation. We suggest that you write down the reasons for your answer.

  1. How does the yield change when the recycle ratio increases?

This Demonstration shows mass balances for an evaporative crystallization process. A 40% KCl/60% H2O feed is mixed with a recycle stream and fed to an evaporator, which evaporates water and increases the KCl concentration in the exiting solution. This solution enters a crystallizer and filter. A filter cake of KCl crystals and a portion of the saturated KCl solution are removed from the crystallizer and filter. The rest of the KCl solution is recycled and mixed with the fresh feed. The fraction of the crystals in the product stream can be varied. The temperatures of the evaporator crystallizer/filter can also be varied, and the solubility of KCl increases linearly with temperature.

Try to answer these questions before determining the answer with the simulation. We suggest that you write down the reasons for your answers.

  1. How does increasing the temperature of the evaporator affect the amount of KCl crystals leaving the process?
  2. How does increasing the temperature of the crystallizer and filter affect the amount of KCl crystals leaving the process?