Calculation of the heat released upon dissolving sodium hydroxide
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13.3 kilograms of sodium hydroxide are dissolved in 31 kilograms of water. According to Figure 4-1-21 in the Chlor-Alkali Industry Manual, the integrated heat of dissolution for 30% solutions is 278 kcal/kg; thus, the heat of dissolution calculated is 15480 kJ. Table 5.2.32 of the inorganic volume of the material property data handbook shows that at 18°, the solubility is 30.75%, with a heat of solution of 46306 J/mol; thus, the calculated heat amount is 15398 kJ. The two results are very close. However, when using Aspen for simulation calculations, the dissolution heat at 18° is 7390 kJ. Please advise, experts
Have you considered the heat from heating the solution? 7390 kj+ If you cool the solution to 18°C, it might become consistent
After the two streams are mixed in a mixer, they are cooled to 18 degrees Celsius using a heat exchanger; the heat of mixing is 14,328.9 kJ/hr, or 257.32 kcal/kg. For the thermodynamic approach, just choose an electrolyte.
We used the electrolyte method, but our simulation results were different. However, after removing sodium hydroxide with one molecule of crystal water, the results obtained from re-simulation were quite similar. What could be the reason for this?
I checked Volume 1 of the Petrochemical Design Manual, page P259; the dissolution heat of sodium hydroxide containing water is approximately half that of anhydrous sodium hydroxide. It seems that the data referred to were for anhydrous sodium hydroxide, yet the simulation used sodium hydroxide containing water