batch steam distillation

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Pamantasan ng Lungsod ng Maynila

College of Engineering and Technology

Department of Chemical Engineering

BATCH DISTILLATION COLUMN

DESIGN DESCRIPTION

The design of the distillation column is held on the basis of separating the

components of the hydrated feed, mainly levulinic acid and formic acid. The

operation of the distillation column will undergo a batch process. Steam will be

used as medium that will heat the mixture at 150 0C. Levulinic acid is then

collected as the bottoms product while formic acid is the distillate.

DESIGN SELECTION

Batch steam distillation is used since it is more economical than other

various types of distillation especially when dealing with only two components

having different boiling points.

DATA AND ASSUMPTIONS

1. The feed to the column is a homogenous liquid and enters the column at70C

2. The rate of feed entering is 228.74 kg/batch. (Based from materialbalance)

3. Amount of distillate is 64.944 kg/batch of formic acid and the bottomsproduct is 163.8 kg/batch levulinic acid.

4. The density of formic acid is 1220 kg/m3 and that of levulinic acid is 1134kg/m3.

5. The molecular weight of formic acid is 46.03 g/mol and that of levulinicacid is 116.13 g/mol

6. Cp of formic acid = 2.151 kJ/kg-K, Cp of levulinic acid = 3.0235 kJ/kg-K7. Assume ideal mixture


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DESIGN CONSIDERATIONS

1. Assume overall heat transfer coefficient = 300 BTU/ft2-hr-F (table 11.2,page 333, Unit Operations of Chemical Engineering by McCabe, Smith

and Harriott).

2. Holdup is negligible (Page 13-96 Perrys Chemical Engineers Handbook7th Edition)

3. Column is operating at 1500C4.

Operation is within 45 minutes

5. Safety factor is 30%DESIGN REQUIREMENTS

1. Volume of column2. Column diameter3. Column height4. Heating surface area5. Shell Thickness6. Head and bottom thickness7. Steam requirement


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DESIGN CALCULATION

1. Column DiameterThe total feed is 228.74 kg/batch, the volume of the fluid can be solved using

the density:

The vaporization rate C is

The equivalent volume of this vaporization rate can be solved using ideal gas

law;

The average molecular weight of this solution is

The total volume of this mixture is then


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Applying 30% safety factor

2. Column diameter

Use the formula of the volume of sphere to solve the equivalent diameter

D = 2.21642 m

Use D = 2.5 m

3. Column height

4. Heating surface area

Where:

U = overall heat transfer coefficient


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A = heating surface area

= mean temperature difference

( )

Q = 50795.741 KJ/ batch (based on energy balance)

Applying 30% safety factor

5. Shell thickness

Using equation 43, Process Equipment Design by Hesse

Where:

tS = thickness of the plate

p = Internal Pressure


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D = Internal Diameter

S= Allowable Working Stress

E = Efficiency

C = Corrosion Allowance

To solve the value of S:

Use equation 41, Process Equipment Design by Hesse

S = (SU)(Fm)(Fa)(Fs)

Where:

SU = 11000 psi (Table 3.1, Process Equipment Design by Hesse)

Fm = 1.00 for high tensile strength carbon steels

Fa = Fr =1.00 since radiographing and stress relieving is not required

Fs = 0.25 (Table 4.2, Process Equipment Design by Hesse)

Therefore:

S = 11000 x 1.00 x 1.00 x 1.00 x 0.25 = 2750 Psi

Solving the internal pressure, p:


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Assume C = 1/16

tS = 0.0676 in = 1.7172 mm

Use thickness = 2.0 mm

6. Head and Bottom Thickness

Use equation 4 8 of Process Equipment Design by Hesse for hemisphericalhead and bottom:

t = 0.0657 in = 1.67 mm

Use thickness = 2.0 mm

7. Steam requirement

Based on energy balance

S = 36.1278 kg/batch


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DESIGN SPECIFICATIONS

Distillation ColumnIDENTIFICATION

ITEM: Batch Steam Distillation column

NUMBER OF REQUIRED UNITS: 1

MATERIALS HANDLED: (based on Levulinic acid heavy key)

FUNCTION: To separate levulinic acid from formic acid

MATERIALS OF CONSTRUCTION: 9Ni carbon steel alloy

DESIGN DATA

PARAMETERS PROPOSED DESIGN

Dimensions:

Volume

Height

Diameter

7.41 m3

5 m

2.5 m

Shell thickness 2.0 mm

Head and bottom

thickness2.0 mm

Heating Surface Area 0.29 m2


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DESIGN CONFIGURATION

Shell Thickness

2 mm

5 m

2.5 m

Head and bottom thickness

2 mm

batch steam distillation

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