Question

Please help with this question regarding the design of a forward-feed double effect evaporator. Will really appreciate it.

(I've edited by typing out the questions, so the question is now clearer.)

Please provide a proposal for the design of a forward-feed double effect evaporator (Figure 1), for which operating conditions are given below.

    Figure 1: Schematic diagram of forward-feed double effect evaporator

Configuration: Forward-feed double effect evaporator

Number of effects: 2

Feed:

Feed material: Aqueous high molecular weight solution

Flow rate: 8000 kg hr^-1

Concentration: 5% aqueous high molecular weight solution

Temperature: 40°C

Discharge:

Product material: Concentrated high molecular weight solution

Concentration: 40% caustic soda solution

The last effect will be assumed to operate at a vacuum of 600 mm Hg referred to a 760 mm Hg barometer

Estimated Overall heat transfer coefficients:

550 kcal hr^-1 m^-2 °C^-1, and 370 kcal hr^-1 m^-2 °C^-1 in effects 1 to 2, respectively.

Utilities:

Saturated steam at 3.5 kg·cm^-2 gauge pressure is to be used for heating. The condensate from each effect leaves at its saturation temperature, negligible radiation losses.

Perform following tasks.

1. Perform overall material balance and overall component material balance, and find mass of steam, mass of evaporation rate in the first and second effects (ms₁ & ms₂).

2. Do energy / enthalpy balance and find solution temperature and vapour space temperature in each effect. Also need enthalpy distribution. Assume negligible boiling point elevation. Assume average specific heat of 1 kcal·kg^-1°C^-1 in the first effect and 0.94 kcal·kg^-1°C^-1 in the second effect. Necessary data may be obtained from steam table.

3. Calculate areas in each effect (deviation in area is within ±10% is acceptable).

4. Calculate steam consumption and analyze operational economy.

5. Recommended number of tubes required for the purpose tube numbers and principal dimensions (such as height, diameter, down take area, actual area). Given height and outer diameter of each tube are 12 ft and 42.16 mm, respectively.

The picture below is the original image (unclear).

Vopour from first effect Vapour from second effect msl ms2 Steam Condensote Condensote Concentrate Concentrate from first effect Please provide a proposal for the design of a forward-feed double effect evaporator (Figure 1), for which operating conditions are given below. Figure 1: Sehematie diagram of forward-feed double effeet evaporator Configuration: Forward-feed double effect evaporator Number of effeets: 2 Feed Feed matcrial: Aqueous high molecular weight solution Flow rate: 8000 kg hr Concentration: 5% aqueous high molecular weight solution Temperature: 40 °C Dischargc Product material: Concentrated high molecular weight solution Concentration: 40% caustic soda solution The last effect will be assumed to operate at a vacuum of 600 mm Hg referred to a 760 mm Hg barometer S0 keal hr2o and 370 keal hr o ineffects 1 to 2, respectively. Utilities: Saturated steam at 3.5 kg.cm gauge pressure is to be used for heating. The condensate from cach effect leaves at its saturation temperature, negligible radiation losses Perform following tasks. 1. Perform overall material balance and overall component material balance, and find mass of steam, mass of evaporation rate in the first and second effects (ms&ms) 2. Do energy enthalpy balance and find solution temperature and vapour space temperature in each effect. Also need enthalpy distribution.Assume negligible boiling point elevation. Assume average specific heat of I kcal.kg1 C 'in the first effect and 0.94 kcal.kg C in the second effect. Necessary data may be obtained from steam table. 3. Calculate areas in each effect (deviation in area is within 10% is acceptable). . Calculate steam consumption and analyze operational economy. S. Recommended number of tubes required for the purpose tube numbers and principal dimensions (such as beight, diameter, down take area, actual area). Given height and outer diameter of each tube are 12 and 4216 mm, respectively

Answer 1

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Chast No 1300 1200 1100 1000 900 210°C(483 К) 800 185°C(458 K) 160 C(433 K) 135°C(408 К) 110°C(383 К) 85°C(358 K) 700 600 500 400 300 60°C(333 К) 35 C(308 K) 200 100 10°C(283 К) 0°C(273 К) -100 5 10 15 20 25 30 35 40 45 50 55 60 65 70 80 NaOH, mass % (^^' Enthalpy Concentration Diagram NaOH - Water System Enthalpy, kJkg solution 75