Intermittent reaction problem

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Friends, I have a question regarding the RBatch batch reaction module in Aspen that I’m not quite sure about. The details are as follows; please help me out: 1. I created a batch reaction process for the reaction of CO2 with EO to produce EC. (1) The one-time addition amount of EO is 1 kmol (i.e., 44 kg) ； CO2 is added continuously, with an initial flow rate of 1 kmol/h ； (2) The reaction temperature is set at 130℃ ； (3) For the reaction pressure, select “calculate reactor pressure” on the setup page, and set the pressure value to 25 bar through the “controller” ； (I understand that the software should achieve this set value by adjusting the CO2 flow rate of the continuous feed.) ； (4) The reactor uses the predefined kinetic equation ； (5) Set the reactor volume to 1000L/800L/500L, and then check the calculation results. 2. Set the reaction volume to 1000, 800, and 500 L (with all other conditions remaining unchanged), and then check the calculation results, as follows: 3. The problem is that I don’t quite understand the calculation results. For example, after a reaction time of 2 hours, the EO conversion rates for reactors with volumes of 1000 L, 800 L, and 500 L were 63%, 71%, and 80% respectively. Why are the reaction results (EO conversion rates) different depending on the reactor volume? I’m not very good at understanding chemical reactions; I hope everyone can give me some guidance.