The issue of expanded diameter at the outlet of the vacuum furnace
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The book states that \"a pressure-reduction furnace needs to inject a certain amount of water vapor at the vaporization point of the oil, in order to reduce the partial pressure of the oil and enable the feed to reach the desired vaporization rate at the specified temperature.\" Does this mean that vaporization occurs only when steam is injected? What does oil partial pressure mean? If the oil does not expand in diameter or expands insufficiently after reaching its boiling point, the temperature of the oil inside the furnace will be higher than the outlet temperature, leading to decomposition. How can the temperature inside the furnace be higher than the outlet temperature? Thank you to the teachers for their guidance
Does vaporization occur only when steam is injected? Oil is a mixture; when heated, the lighter components vaporize first, while the heavier components are less likely to vaporize. The purpose of injecting steam is to facilitate the vaporization of these heavier components, or in other words, to promote the vaporization of the heavier oil components； What causes steam injection to promote the vaporization of the heavier components? It is because the partial pressure of oil and gas decreases after steam injection. Simply put, before injection there were only oil and gas vapors, but now water vapor is also present; therefore, the partial pressure of oil and gas becomes Voil/(Voil+Vw). Without steam injection, the partial pressure of oil and gas is Voil/Voil, which is 100%. How can the temperature inside the furnace be higher than the outlet temperature? The furnace tubes contain a mixture of oil and gas; if the vaporization rate of this mixture increases, it indicates that there is a relatively larger proportion of gaseous components in the feed, with fewer liquid components. The gaseous components originate from the liquid components that have absorbed heat. Therefore, it can be said that the conversion of liquid oil into gaseous form absorbs latent heat, which results in a lower temperature at the furnace outlet. This is why the temperature inside the furnace is higher than the outlet temperature. The original poster could take a closer look at the sections under \"Principles of Chemical Engineering\" and \"Technical Questions and Answers on Atmospheric and Vacuum Distillation Units\"
Thank you. What the person upstairs said helped me understand right away. I get it. Thank you again