Lab Engineering 4-Lab 2

8/10/2019 Lab Engineering 4-Lab 2

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1.0 PROCEDURE

The production of methanol is carried out in a moderate-pressure synthesis loop by direct

hydrogenation of carbon dioxide, which generates a liquid product that contains a binarymixture of methanol and water in approximately equal proportions. To provide commercial

methanol that is nearly free of water, dehydration is achieved commonly by distillation. The

simulation considered an equimolar mixture of 2700 kmol/hr at 25 oC and 5.2 bar. It is then

split and fed to two distillation columns, one at reduced pressure, with the design

specification shown in the following table:

Condition DC 1 DC 2

Pressure (bar) 5.2 1.01

Number of trays 16 13

Feed Tray* 12 9

Reflux ratio 1.26 0.834

Distillate to feed ratio 0.96 0.96

*Count from the top of DC

To start the design, Advanced Peng-Robinson property package was selected with the split

ratio for DC properties is 0.5 and total condenser for both DC was used. Every stream was

created and entered with specific details. The properties for both DC were entered with

information from the table above.


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2.0 PROCESS FLOW DIAGRAM

Figure: Process Flow Diagram


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3.0 WORKBOOK

Name FEED S1 S2 S3

Description

Upstream Op

C-

2.LiquidDraw_0_condenserL SP-1.Out1 SP-1.Out0

Downstream Op SP-1.In C-2.Feed_11_feed Vlv-1.In

VapFrac 0.00 0.00 0.00 0.00

T [C] 25.0 123.4 25.0 25.0

P [kPa] 520.00 520.00 520.00 520.00

MoleFlow/Composition Fraction kgmole/h Fraction kgmole/h Fraction kgmole/h Fraction kgmole/h

METHANOL 0.5000 1350.00 0.52083 675.00 0.5000 675.00 0.5000 675.00

WATER 0.5000 1350.00 0.47917 621.00 0.5000 675.00 0.5000 675.00

Total 1.00 2700.00 1.00 1296.00 1.00 1350.00 1.00 1350.00

Mass Flow [kg/h] 67577.14 32815.71 33788.57 33788.57

Volume Flow [m3/hr] 78.814 42.830 39.407 39.407

Std Liq Volume Flow [m3/hr] 78.706 38.379 39.353 39.353

Std Gas Volume Flow

[SCMD] 1.5351E+6 7.3686E+5 7.6757E+5 7.6757E+5

Energy [W] -2.287E+7 -7.708E+6 -1.144E+7 -1.144E+7

H [kJ/kmol] -30494.8 -21410.5 -30494.8 -30494.8

S [kJ/kmol-K] 82.041 108.113 82.041 82.041

MW 25.03 25.32 25.03 25.03

Mass Density [kg/m3] 857.4204 766.1823 857.4204 857.4204

Cp [kJ/kmol-K] 85.760 98.478 85.760 85.760

Thermal Conductivity [W/m-

K] 0.2885 0.2555 0.2885 0.2885

Viscosity [Pa-s] 6.9255E-4 2.0677E-4 6.9255E-4 6.9255E-4

Molar Volume [m3/kmol] 0.029 0.033 0.029 0.029

Z Factor 0.0072 0.0062 0.0072 0.0072

Surface Tension

Speed of Sound


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Name S4 S5 S9 S10

Description

Upstream Op Vlv-1.Out

C-

2.LiquidDraw_15_reboilerL

C-

1.LiquidDraw_0_condenserL

C-

1.LiquidDraw_12_reboilerL

Downstream Op C-1.Feed_8_feed

VapFrac 0.00 0.00 0.00 0.00

T [C] 25.1 153.1 73.0 99.9

P [kPa] 101.00 520.00 101.00 101.00

MoleFlow/Composition Fraction kgmole/h Fraction kgmole/h Fraction kgmole/h Fraction kgmole/h

METHANOL 0.5000 675.00 0.00005 0.00 0.52083 675.00 0.00001 0.00

WATER 0.5000 675.00 0.99995 54.00 0.47917 621.00 0.99999 54.00

Total 1.00 1350.00 1.00 54.00 1.00 1296.00 1.00 54.00

Mass Flow [kg/h] 33788.57 972.86 32815.74 972.83

Volume Flow [m3/hr] 39.416 1.063 40.194 1.015

Std Liq Volume Flow [m3/hr] 39.353 0.974 38.379 0.974

Std Gas Volume Flow

[SCMD] 7.6757E+5 3.0703E+4 7.3686E+5 3.0703E+4

Energy [W] -1.144E+7 -3.684E+5 -9.413E+6 -4.316E+5

H [kJ/kmol] -30494.8 -24559.9 -26146.4 -28770.0

S [kJ/kmol-K] 82.089 98.409 95.395 87.885

MW 25.03 18.02 25.32 18.02

Mass Density [kg/m3] 857.2303 915.2577 816.4430 958.8348

Cp [kJ/kmol-K] 85.788 81.193 90.111 77.495

Thermal Conductivity

[W/m-K] 0.2885 0.6814 0.2740 0.6791

Viscosity [Pa-s] 6.9104E-4 1.7854E-4 3.4650E-4 2.8199E-4

Molar Volume [m3/kmol] 0.029 0.020 0.031 0.019

Z Factor 0.0014 0.0035 0.0013 0.0007

Surface Tension

Speed of Sound


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4.0 QUESTIONS AND DISCUSSIONS

1. What is the molar flow before entering DC1 and DC2?

The molar flow before entering the DC1 and DC2 is 1350 kgmole/hr. The feed molar flow

was 2700 kgmole/hr. The molar flow was divide by two as there were splitter placed before

the DC1 and DC2.

2. How to reduce pressure in DC2?

To reduce the pressure in DC2 a valve was place before the stream enter the DC2.

3. What is the temperature at the bottom of DC1 and DC2?

The temperature at the bottom of DC 1 is 153.0554C and temperature at the bottom of DC2

is 99.918C.Temperature and pressure are directly proportional to each other. This means

that as the temperature decreases, the pressure also decreases, and as the temperature

increases, the pressure increases.

4. Did the process achieve a methanol that free from water? What is the purity of the

methanol? How to increase the purity?The process did not achieve a methanol that free from water. There is still fraction of water in

the stream. The purity of the methanol is 0.96. It is impossible to achieve methanol that is

free from water if they only go through DC once. A recycle stream should be put at the

output and the stream goes back to the feed stream, so they go through the distillation

process again. Besides that, adding some more of DC in parallel series so it could help to

achieve a methanol that free from water as the product goes through the distillation process

several times. Moreover, place an evaporator at the product stream could help achieving a

methanol that free from water. The evaporator helps to evaporate water inside the product

stream then the stream is recycle back into the feed stream to go through the distillation

process again.

Lab Engineering 4-Lab 2

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