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This post was last edited by yggswl on 2017-6-3 20:41. I have a question: How much heat is required to vaporize 100 kg of ammonia solution with a concentration of 20% at 20°C, completely to a temperature above 100°C? Could you please provide the calculation process? Thank you everyone!
What is the ammonia concentration? Why not use liquid ammonia?
To ask this question, there needs to be pressure and concentration, you know
I’m sorry; it’s ammonia solution with a concentration of 20%, at atmospheric pressure
For denitration; it is necessary to vaporize ammonia water
When 1 kg of ammonia at 100°C turns into steam at the same temperature, the heat absorbed for vaporization is 539 calories, and this value depends on the temperature.
When 1 kg of ammonia at 100°C turns into steam at the same temperature, the heat absorbed for vaporization is 539 calories, and this value depends on the temperature.
Here are my calculations; please take them as a reference! Calculation of the heating energy required for the ammonia solution in the evaporator: Ammonia requirement = 100.00 kg/h. The weight percentage of ammonia is 20%, so the amount of ammonia = 20.00 kg/h, while the amount of water = 80.00 kg/h. The heating temperature ranges from 20 ℃ to 100 ℃. The boiling point of ammonia is 38 ℃, and that of water is 100 ℃. The specific heat capacity of liquid ammonia is 4.325 kJ/kg·K, and its vaporization heat is 1731 kJ/kg. The specific heat capacity of ammonia vapor is 2.5852 kJ/kg·K. The energy required to heat the ammonia solution to its boiling point is 7785 kJ/h. The energy needed to convert the ammonia solution into ammonia vapor is 34620 kJ/h. The energy required to heat the ammonia vapor to the desired temperature is 3206 kJ/h. The specific heat capacity of water is 4.184 kJ/kg·K, and the latent heat of vaporization of water is 2675 kJ/kg. The specific heat capacity of water vapor at 1.1 BarG is 2.05 kJ/kg·K. The energy required to heat water to its boiling point is 26778 kJ/h, and the energy needed for water to evaporate is 214000 kJ/h. The energy required to heat water vapor to the desired temperature is 0 kJ/h. The total heating energy required is 286388 kJ/h, which is equivalent to 68416 kcal/h, or 80 kW
The calculations upstairs are detailed but incorrect; they fail to take into account that the reaction of ammonia in water generates heat amounting to 4757 kJ/kg. Additionally, when denitration takes place, the ammonia is injected in gaseous form, so all the water should evaporate. Simplified algorithm: The heat absorbed during the dissociation of 20 kg of ammonia is 20*4757=95140 KJ/h. The heat required to vaporize 80 kg/h of water is 80*2250=180000 KJ/h. To raise the temperature of 20 kg of ammonia from 20 degrees to 100 degrees, 20*4.325*80=6920 KJ/h is needed. The heat required to raise the temperature of water is 80*4.18*80=26752 KJ/h. The total amount of heat is 308812 KJ/h, which corresponds to 85.8 KW. This is a rough algorithm; it ignores factors such as specific heat and enthalpy related to temperature changes. It serves as a reasonable baseline for heat calculation during design. The area of the heater calculated in this way should be increased by 25–40%, as room needs to be left for adjusting the amount of ammonia used.