Fluidized-Bed Drying Technology for Trisodium Phosphate

Trisodium phosphate is also known as sodium phosphate. In cleaning agents, it can be used as a corrosion inhibitor for copper or steel. It possesses some emulsifying properties and can be considered the best detergent for removing dirt from metal surfaces. When manufacturing trisodium phosphate, the moisture content must be reduced from 5% to approximately 0.5%. Selecting the appropriate drying equipment is crucial for trisodium phosphate. We have selected a vibrating fluidized bed dryer for drying trisodium phosphate.

  Changzhou Yidu Drying Equipment Co., Ltd. has performed the following calculations based on the relevant parameters of this material:

  a Heat of dehydration: Q1 = W_water (595 + 0.46 × t₂ − 1 × θ₁) = 5.4680 × 10⁴ kcal/h

  b Heat required to raise product temperature: Q2 = W_(product) × [0.35 × (1 – ω₂) + 1 × ω₂] × (θ₂ – θ₁) = 1.3490 × 10⁴ kcal/h

  c Heat loss through equipment insulation: Q3 = 0.2 × (Q1 + Q2) = 1.3634 × 10⁴ kcal/h

  d Mass flow rate calculation: G = (Q1 + Q2 + Q3) / (i1 - i2 - 0.1 × 0.24 × (t2 - t0)) = 16,764 kg/h [i1 - i2 = 4.879 kcal/kg]

  e Heat required for drying: Q_(dry) = G × (i₁ − i₀) = 16.09 × 10⁴ kcal/h

Based on practical experience with similar materials in vibrating fluidized bed production, the drying time for the material in this equipment is set at 5 minutes, with an average bed depth of 4–6 cm; the perforation rate of the fluidized bed tray and the perforation gas velocity are generally controlled at 3–10% for the perforation rate and 10–16 m/s for the perforation gas velocity. For ammonium sulfate-type materials (which have a high specific gravity and low dehydration rate), the perforation gas velocity is set to 12–13 m/s (taken as 12.5), while the bed plate open area ratio ε is set to 4.2–5%; The logarithmic mean temperature difference of superheated steam, Δtm, is ((tb - t0) - (tb - t1)) / ln((tb - t0) / (tb - t1)) = 75.9°C; Based on experience, the heat transfer coefficient of the heater is taken as K = 9 kcal/m²·h·°C (the heat transfer coefficient of superheated steam is relatively low), so the heat exchange area is F = Q / (K × Δtm) = 150 m². An SRZ-type heat exchanger is selected, with the SRZ10×6D model as the preliminary choice. One set of cyclone separators is provided. A long-cone-type cyclone separator, model CZT950, which is effective for separating fine dust at low concentrations, is selected, with two units connected in parallel. The total air volume for the single drying bed system (drying air L_dry and cooling air L_cool) is L_dry = 12.5 × 3600 × 7.5 × 4.2% = 14,175 m³/h; The total induced draft airflow, L_(ind), is approximately 16,500 m³/h. One blower is used for the drying hot air, model 4-72 6C, 15 kW; one induced draft fan is used, model 9-26 9D, 37 kW. The heat required by the system based on the system airflow rate: Q = 19.08 × 10⁴ kcal/h (assuming an inlet air temperature of 50°C).