For concentrating an aqueous solution of a material like anhydrous Na2SO4, whose solubility decreases with rise in temperature, the most suitable evaporator is a _______________ evaporator?

Related Mcqs:

1. It is desired to concentrate a 20% salt solution (20 kg of salt in 100 kg of solution) to a 30% salt solution in an evaporator. Consider a feed of 300 kg/min at 30°C. The boiling point of the solution is 110°C, the latent heat of vaporisation is 2100 kJ/kg and the specific heat of the solution is 4 kJ/kg.K. The rate at which the heat has to be supplied in (kJ/min) to the evaporator is____________________?

   A. 3.06 × 105
   B. 6.12 × 105
   C. 7.24 × 105
   D. 9.08 × 105

2. An evaporator while concentrating an aqueous solution from 10 to 40% solids evaporates 30000 kg of water. The amount of solids handled by the system in kg is___________________?

   A. 4000
   B. 9000
   C. 4600
   D. 3000

3. A dilute aqueous solution is to be concentrated in an evaporator system. High pressure steam is available. Multiple effect evaporator system is employed, because__________________?

   A. Total heat transfer area of all the effects is -less than that in a single effect evaporator system
   B. Total amount of vapor produced per Kg of feed steam in a multiple effect system is much
   higher than in a single effect
   C. Boiling point elevation in a single effect system is much higher than that in any effect in a
   multi-effect system
   D. Heat transfer co-efficient in a single effect is much lower than that in any effect in a multieffect
   system

4. Agitated film evaporator is suitable for concentrating _____________ liquids?

   A. Foaming
   B. Viscous
   C. Very thin
   D. Corrosive

5. A multiple effect evaporator has a capacity to process 4000 kg of solid caustic soda per day, when it is concentrating from 10% to 25% solids. The water evaporated in kg per day is__________________?

   A. 6000
   B. 24000
   C. 60000
   D. 48000

6. A backward feed multiple effect evaporator is better than forward feed for concentrating cold feed, because it provides __________________?

   A. Higher economy
   B. Lower capacity
   C. Both A. & B.
   D. Lower economy

7. A multiple effect evaporator as compared to a single effect evaporator of the same capacity has _________________?

   A. Lower heat transfer area
   B. Lower steam economy
   C. Higher steam economy
   D. Higher solute concentration in the product

8. In a single evaporator system, the steam economy ________________ by creating vacuum in the evaporator?

   A. Increases
   B. Decreases
   C. Remain constant
   D. May increase or decrease, depends on the vacuum

9. For the same heat transfer area and the terminal conditions, the ratio of the capacities of a single effect evaporator to a triple effect evaporator is_________________?

   A. 3
   B. 0.33
   C. 1
   D. 1.33

10. Steam consumption in kg/hr in case of an evaporator is given by (where, C & E are capacity the economy of the evaporator respectively) ?

    A. C/E
    B. E/C
    C. CE
    D. 1/CE