Discussion on on-site heat exchange issues
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The unit was started up on Friday; water is currently being used for operation. V301 is the acrylonitrile evaporation tank (with hot water in the jacket and coiled tubes), and water is now used in its place to assess its load. The water flow rate into the evaporation tank is 380 KG/H, which is just enough to maintain balance； Operating conditions: pressure of -68 KPA, temperature of 71 degrees; 80-degree hot water flows through the coil, while 2 kilograms of steam flows through the jacket ； The designed feed rate of acrylonitrile to the evaporation tank is 500 KG/H, with hot water flowing through both the jacket and the coils. Is this current operating condition sufficient to meet the requirements? I have the following data: the latent heat of steam is 550 KCAL/KG, and that of acrylonitrile is 150 KCAL/KG. Based on these figures, my calculation shows that 550*380/150 = 1400 KG/H, which is far above the designed value. This evening, my supervisor suggested using hot water at 80 degrees instead of steam for heating the evaporation tank, and asked me to determine what flow rate of water in the evaporation tank would be necessary to achieve the designed flow rate for acrylonitrile. My calculation gives 500*150/550 = 136 KG/H. Please let me know if this approach is correct!
I. Few parameters: 1. The temperature at which steam needs to be condensed; 2. The temperature after the water has been cooled. II. Calculation method: +380 X = the enthalpy of the steam at the condensation temperature. For the value of 550, it is best to use the enthalpy value of steam in this state, Y = the temperature at which water condenses.
What you mean is to use 80-degree hot water instead of steam for heating. The other parts remain unchanged; you only need to calculate the heat released by the steam, and this heat is the amount of heat that needs to be released using water at 80 degrees Celsius. Assuming that the heat released by the steam is its latent heat, which is 500 kcal/kg, and the rate at which steam is released is 2 kg/h, then the heat released is 1000 kcal/h. Using the formula 1000 = C_water * m_water * ΔT_water, the value of m_water gives the mass flow rate of water. Of course, it would be better if one could determine the enthalpy values before and after the steam passes through a heating element; that would provide more accurate results. Just knowing the latent heat alone isn’t sufficient. This post was last edited by ajie8352 on 2009-3-17 at 19:19