New substances have been added to the Aspen material library, resulting in different simulation outcomes
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I want to know the boiling point of a mixed solution of sulfuric acid an and ammonium dihydrogen phosphate at atmospheric pressure； First, I added the anhydrous sulfuric acid component to the material library and set up the ionization reaction ； In the FLOW SHEET, 55% sulfuric acid solution was set as the feed, resulting in a boiling point of 107°C, which is generally consistent with the values reported in the literature ； After that, I added the ammonium dihydrogen phosphate component to the material library and set up the ionization reaction ； After that, run FLOWSHEET again (note that the feed composition has not changed; it remains 55% sulfuric acid an), and the simulated boiling point becomes 104°C at this point. . . The physical property data before and after were compared one by one, and no issues were found. . Please ask an expert for help. Note: The property equations used are all from ELECNRTL; other property equations for ionized substances have also been tried, but none of them work
Later I removed ammonium dihydrogen phosphate, and the simulated temperature was still 104°C; I guess the properties of sulfuric acid AN changed after new substances were added； I conducted two simulations (one with ammonium dihydrogen phosphate added and one without), and there was no difference in the property data for sulfuric acid and its corresponding salt ions in the reviews for both
Strange. I couldn’t figure it out yesterday at all, but I understood it right after posting this thread. . . That is, I first set up the ionization equation for sulfuric acid, and later added the ionization equation for ammonium dihydrogen phosphate. . That’s the problem: since the ionization equation already existed earlier, Aspen prompted me to overwrite the existing one. I clicked “Yes”, and as a result, all the chemical equations in Chemistry–Global were replaced by the ionization equation for ammonium dihydrogen phosphate; in other words, sulfuric acid no longer appeared as an ionizable substance ； At this point, whether you remove the ammonium dihydrogen phosphate component or change its physical properties, the simulation results will be incorrect, because Aspen assumes by default that sulfuric acid does not ionize at this stage. . . . I later just set the ionization using both salts together ； Or, you can also manually set the ionization equation in chemistry--global