An evaporator is used to concentrate 4536 kg/hr (10,000 lb/h) of a 20% solution of NaOH in water entering at 600C (1400F) to a product of 50% solids. The pressure of the saturated steam used is 172.3 kPa (25 psia) and the pressure of the vapor phase in the evaporator is 11.7 kPa (1.7 psia). The overall heat transfer coefficient is 1560 W/m2-K (275 BTU/h-ft2 – 0F). Calculate for the steam used, steam economy, and heating surface area. Required: ____________, _____________, _______________ Solution: 1. Calculate the amounts of the L and V phase products using the material balance equations. 2. From steam tables the boiling point of pure water at 11.7 kPa is _____________ 3. From the HANDBOOK Chart the boiling point rise is _______________ and consequently the boiling point of the solution is ______
An evaporator is used to concentrate 4536 kg/hr (10,000 lb/h) of a 20% solution of NaOH in water entering at 600C (1400F) to a product of 50% solids. The pressure of the saturated steam used is 172.3 kPa (25 psia) and the pressure of the vapor phase in the evaporator is 11.7 kPa (1.7 psia). The overall heat transfer coefficient is 1560 W/m2-K (275 BTU/h-ft2 – 0F). Calculate for the steam used, steam economy, and heating surface area.
Required: ____________, _____________, _______________
Solution:
1. Calculate the amounts of the L and V phase products using the material balance equations.
2. From steam tables the boiling point of pure water at 11.7 kPa is _____________
3. From the HANDBOOK Chart the boiling point rise is _______________ and consequently the boiling point of the solution is _______________
4. From the enthalpy-concentration chart of NaOH in the Handbook the enthalpy of the feed is _____________ and the enthalpy of the liquid product is _______________.
5. From steam tables the latent heat of condensation of the condensing saturated steam is ______________.
6. From steam tables the enthalpy of the vapor product is ________________.
7. The adjusted enthalpy of the vapor product due to boiling point rise can be calculated.
8. The amount of steam can be calculated using the enthalpy balance equation.
9. The steam economy can be calculated
10. The amount of heat transferred through the heat transfer area A can be calculated.
11. The heat transfer area can now be calculated using the design equation for heat transfer equipment
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