Process calculations and verification for the glass-fiber reinforced plastic cooling tower in the phosphoric acid workshop

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Regarding the process calculations and verification for the glass-fiber reinforced plastic cooling tower in the phosphoric acid plant: I. One calculation method: Data is taken from the calculation conducted by Engineer Wu, titled \"Thermal Calculation for the Wet Process of Concentrating P2O5 with a daily production capacity of 180 tons.\" The heat that needs to be removed for cooling 1000 kilograms of P2O5 under low-vacuum conditions is (1734915 KJ/h) and (1850576 KJ/h). 2. At 180 tons of P2O5 per day, the hourly production of P2O5 is 7.5 tons ； 3. Heat to be removed for P2O5 production at 7.5 tons per hour using low-vacuum cooling: = 1850576 KJ/h × 7.5 = 13011862.5 KJ/h = 1.388×107 KJ/h.
II. Two calculation methods:
Heat to be removed for low-vacuum cooling: The slurry circulation rate in the low-vacuum cooling system is 1000 m3/h, with an inlet temperature of 74°C and an outlet temperature of 70°C. The specific heat capacity of the slurry is CP = 2.2386 KJ/Kg·°C. The heat removed by low-vacuum cooling is △Q = 1000 × 1.55×103 × 2.2386 × 4 = 13879320 KJ/h = 1.388×107 KJ/h.
III. Three calculation methods:
Heat to be removed for low-vacuum cooling: The slurry circulation rate in the low-vacuum cooling system is 1000 m3/h. Assuming an inlet temperature of 76°C and an outlet temperature of 70°C, with a specific heat capacity of CP = 2.2386 KJ/Kg·°C; (since the temperature readings in our company were incorrect and showed negative values, we referred to the design manual “Technology and Design Manual for Phosphoric Acid, Phosphatic Ammonium, and Calcium Carbonate”, where a value of 4–6°C is used as a standard, so we used the maximum value of 6°C.) The heat removed by low-vacuum cooling is △Q = 1000 × 1.55×103 × 2.2386 × 6 = 20818980 KJ/h = 2.08×107 KJ/h.
IV. Calculation of the area required for the glass fiber reinforced plastic cooling tower:
1. Assuming the flow rate of the circulation pump is 200 m3/h, with an inlet temperature of T2 and an outlet temperature of 40°C. The specific heat capacity of water is CP = 4.183 KJ/Kg·°C. Q_absorbed = Q Released ； 2.08×107 = 200×1.00×103×4.183 (T2 – 38); the resulting value for T2 is 62.86°C, which is too high – it’s not acceptable. 2. Re-assume the conditions: the temperature at the inlet of the tower is T2=55°C, while the temperature at the outlet is 40°C; thus, ⊿T=15°C. What is the flow rate of the circulation water pump? 2.08×107=Q×1.00×103×4.183×15 ； It is found that Q=331.5 m3/h. 3. Assume new conditions: inlet temperature T2=50°C, outlet temperature=38°C; ΔT=12°C. What is the flow rate of the circulating water pump? 2.08×107=Q×1.00×103×4.183×12 ； The value of Q is 414.36 m3/h; therefore, a water pump with a capacity of 450 m3/h can be used, with a head of 32 meters. The corresponding optional glass fiber reinforced steel tower: 450～500 m3. CHY was calculated on 2007-9-8