# hysys workbook

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• PROCESS SIMULATION CASES 2013

1

HYSYS

WORKBOOK

2013

By: Eng. Ahmed Deyab Fares

• PROCESS SIMULATION CASES 2013

2

Flash Separation

We have a stream containing 15% ethane, 20% propane, 60% i-butane

and 5% n-butane at 50F and atmospheric pressure, and a flow rate of

100lbmole/hr. This stream is to be compressed to 50 psia and then

cooled to 32F (Delta P= 10 kPa). The resulting vapor and liquid are to

be separated as the two product streams.

Fluid pkg: Peng Robinson

Calculate:

- Heat duty rejected from the cooler . kJ/hr

- Compressor Horse Power .

* What are the flow rates and compositions of the two product streams?

Component Vapor Stream Liquid Stream

Ethane (Mole fraction)

Propane (Mole fraction)

I-Butane (Mole fraction)

N-Butane (Mole fraction)

Total Flow rate (kgmole/hr)

* Create a case study to see the effect of changing temperature of

the cooler out stream on the molar flow of the liquid product

• PROCESS SIMULATION CASES 2013

3

Propane Refrigeration Cycle

A Refrigeration cycle utilizes propane as the working fluid is used in

the liquefaction of the NG. Propane is fed to an evaporator (Heater) the

pressure drop=5 kPa, where it absorbed 1.50e+6 kJ/hr from the NG and

leaves at the dew point (Vapor Fraction=1.0) at T= -15oC. The output of

the evaporator is then compressed adiabatically with efficiency of 75%,

and then it's condensed to reject heat. Inside the Condenser there is a

pressure drop of 30 kPa, and leaves as saturated liquid at 45oC. Finally,

the propane passes through a J-T valve to return the pressure of the

Evaporator.

Fluid Pkg: Peng Robinson

Calculate:

Pressure of the evaporator fed in kPa.

Flow rate of propane in kmol/hr.

Valve pressure drop in kPa.

Temperature of the valve outlet in oC.

Compressor duty in hp.

Condenser duty in kJ/hr.

* Calculate the COP (Coefficient of Performance) for the cycle

• PROCESS SIMULATION CASES 2013

4

Refrigerated Gas Plant

This tutorial will model a natural gas processing facility that uses

propane refrigeration to condense liquids from the feed.

The feed stream enters an inlet separator, which removes the free

liquids. Overhead gas from the Separator is fed to the Chiller where it

is cooled to -20oC, which will be modeled simply as a Cooler (Pressure

Drop=35 kPa). The cold stream is then separated in a low-temperature

separator (LTS). Overhead gas from the LTS is fed to the heater

(Pressure drop=5kPa) where it is heated to 10oC to meet Sales Gas

Specifications.

Feed Stream:

Temperature Pressure Molar Flow Rate

15oC 6200 kPa 1440 kgmole/h

Composition:

Mole Component Mole Component

0.0101 n-Butane 0.0066 N2

0.0028 i-Pentane 0.0003 H2S

0.0027 n-Pentane 0.0003 CO2

0.0006 n-Hexane 0.7575 Methane

0.0000 H2O 0.1709 Ethane

0.0001 C7+ (NBP=110oC) 0.0413 Propane

0.0068 i-Butane

FP: Peng Robinson

- Calculate the duty rejected from the chiller

- Calculate the duty Absorbed inside the Heater

• PROCESS SIMULATION CASES 2013

5

Subsequently, the design is modified to reduce the operating cost

represented in Chiller & Heater duties, by adding a Heat Exchanger

before the Chiller where the overhead from the inlet separator is pre-

cooled by already refrigerated gas from LTS.

Heat Exchanger Design Specifications:

- Sales Gas Stream Temperature= 10oC

- Tube side Pressure drop=35kPa

- Shell side Pressure drop= 5kPa

- No heat losses inside the heat exchanger.

- Choose Weighted Exchanger as Model

Calculate the duty rejected from the chiller after this modification . Calculate the Overall Heat Transfer Coefficient (UA) for the HX ..

• PROCESS SIMULATION CASES 2013

6

Heat Exchanger Rating (Gas)

You are asked to find a heat exchanger that will serve as the Gas-Gas

exchanger. However, since you are on a very strict budget, you can only

consider used equipment. A heat exchanger has been found in the surplus

supply of a nearby plant. If the critical process parameter is to maintain a

Sales Gas temperature of at least 10 C (50 F), can this heat exchanger

be used for the Gas-Gas service? The surplus exchanger has been

thoroughly cleaned.

The dimensions of the exchanger are given here:

TEMA: AEL

Tube Length = 1.5 m

Number of tubes = 300

Tube Pitch = 30 mm

Baffle Type = Double

Baffle Orientation = Vertical

Baffle Cut (% Area) = 15%

Baffle spacing = 100 mm

All other parameters are the HYSYS default values

What is the temperature of the Sales Gas using this exchanger?

Note:

- Consider adding Recycle operation - The pressure drops on both sides of the exchanger should be

deleted; this will allow HYSYS to calculate these parameters.

• PROCESS SIMULATION CASES 2013

7

Distillation (1)

We need to separate a mixture of five paraffins into light and heavy

fraction by using a distillation column with 12 trays, a full reflux

condenser, and a Kettle reboiler.

The feed stream (1000 lbmol/hr) consists of 3% (mole %) ethane, 20%

propane, 37% n-butane, 35% n-pentane and 5% n-hexane at 225 oF and

250 psia, which enters the column on the sixth tray, counting from the

top. The condenser and reboiler pressures are 248 and 252 psia,

respectively. The preliminary design specifications require a reflux ratio

of 6.06 and a vapor overhead product of 226 lbmol/hr. Subsequently,

the design is modified to ensure propane overhead flow of 191 lbmol/hr

and n-butane bottom flow of 365 lbmol/hr.

Use SRK Fluid Pkg

Calculate:

The Condenser, the Reboiler Temperatures & the Reflux Ratio after

modification

Condenser Temp oC

Reboiler Temp oC

Reflux Ratio

• PROCESS SIMULATION CASES 2013

8

Distillation (2)

3700 kg/hr mixture of tetrahydrofuran & toluene (44 mass% THF) at 10oC

and 140 kPa is to be separated by distillation to get each of them with

purity of 99.5 mass% of THF & 94 mass% of Toluene (THF is the more

volatile component).

Use Wilson fluid package

The column specifications are:

Number of stages = 10.

Feed enters from the 5th tray.

The condenser works on total condensation conditions.

The condenser & reboiler pressure are 103 kPa & 107 kPa.

Calculate:

The reflux ratio and the distillate rate under the specified

conditions.

Reflux Ratio

Distillate Rate kgmol/hr

Data:

Feed price= 0.05 \$/kg.

Pure toluene selling price= 0.136 \$/kg

Pure THF selling price= 0.333 \$/ kg

Cooling Cost= 0.471 \$/ kw.hr

Heating Cost= 0.737 \$/kw.hr

Note:

Profit = (Total Toluene selling price + Total THF selling price) - (Feed

cost + Heating cost + Cooling Cost)

Use a range of 0.99 to 0.999 for THF limit & 0.9 to 0.99 for the

toluene.

• PROCESS SIMULATION CASES 2013

9

Two Stage Compression

A stream of N.G is fed to a separator at 35oC and 1725 kPa with a flow rate of 11,000

Ibmole/hr where free condensates are separated. The gas is then compressed to 3450 kPa

with adiabatic efficiency of 75% in a centrifugal compressor. The compressed gas is

then cooled to 50oC before entering a second separator where the outlet liquid is then

sent to a valve (delta P= 1725 kPa) and recycled back to the first separator. The outlet

gas is fed to a second compressor where the pressure is doubled and then cooled to

50oC before entering the last separator where the outlet liquid is sent to a second valve

(delta P= 3450 kPa) and recycled back to the second separator.

Notes:

- Neglect the pressure drop inside both coolers.

- Use Mixer to mix the recycled stream with the original feed stream.

- F.PKg : PR

- Composition:

Mole% Component Mole% Component

0.0652 i-Butane 0.0075 N2

0.0578 n-Butane 0.0147 CO2

0.0515 i-Pentane 0.5069 Methane

0.0431 n-Pentane 0.1451 Ethane

0.0357 n-Hexane 0.0725 Propane

Calculate:

- Compressors horse power:

Compressor Horse Power

1 ------------------------------

2 ---------------

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