03-process calculator use illustration

BRIEF USE ILLUSTRATION OF PROCESS CALCULATOR

BY KULDEEP VARMA

MAY 5, 2015

CTAC S5a/a, Plot 14, Chinmay Colony, Karvenagar, Pune 411052.

of 14 – Kuldeep Varma. PROCESS CALCULATOR.

ABOUT PROCESS CALCULATOR

Process calculator is a customized calculator for the

Hydrocarbon Industry which enables an engineer to analyze

any situation from first principles.

Few examples follow.

This is supported by a chartered engineer.

USE LLUSTRATION

Situation 1

A young engineer Rakesh fresh from B.E. Chemical

Engineering joins RIL in Jamnagar and is touring the plant. He

comes near a propane storage vessel and observes that it is a

very hot day. In his course of study he knows that the hotter

the temperature, higher the propane vapour pressure. He

thinks, this system must have been designed when global

warming had not set in. I wonder if this propane vessel is

designed for 48 C which is likely to be today? Otherwise this

vessel can rupture! He observes the mechanical design

pressure of this vessel is 20 Bara and the relief valve is set at

18 Bara. Questions comes to his mind, is this safe at 48 C?


Solution with Process Calculator

1. Click on Component Properties -> Vapor Pressure

2. Select Propane from the drop down box.

3. Enter 48 C in box.


4. Read Vapour Pressure as 16.42 Bar.

Since, the vessel design pressure is 20 Bara and Relief Valve

set pressure is 18 Bara, the young engineer can conclude that

he is safe. The equipment designers have designed the

equipment well!


Situation 2

After his plant tour is over, Rakesh is asked by his senior

engineer Umesh to order 500 kg Nitrogen for flushing a pipe

line. He is given a contact of Linde gas engineer Smitha to

order cylinders.

Rakesh calls Smitha in Linde gas and says I need 500 kg

Nitrogen.

Smitha says, sorry but that is how many cylinders of Nitrogen

sir? One cylinder is 48 L water capacity, 150 Bar Pressure.

Having 7.2 Nm3 gas.



1. Click on Component Properties -> Gas/Vapor Density.

2. Select Nitrogen from the drop down list.

3. Enter Pressure 1 Bar, Temp 0 C, Compressibility 1.

(Compressibility Calculator to be added in future version

of this app.)


4. Read density as 1.251 kg/m3.

5. Hence one cylinder has 7.2 Nm3 gas or 7.2 Nm3 x 1.251

kg/m3 = 9 kg gas.

6. Hence Rakesh should order 500/9 = 56 cylinders.


Situation 3

Plant operator team leader Sujay reported to HOD Mahesh to

investigate a strange phenomenon happening in Ethylene

Plant. In the Ethylene section, when the pressure is 55 Bara

and Temperature is 15 C, operators were saying that the fluid

is neither liquid nor gas. It appears to be strange phase.

Please tell us what is this?


Mahesh knew from his studies that fluid neither being liquid

or gas could be supercritical phase. Is Ethylene in

supercritical phase? He wanted the critical conditions of

ethylene.

1. Go to Component Properties -> Critical Condition.


2. Select Ethylene from drop down list and read Critical

Condition as 282.4 K and 5035.85 kPa.

3. Go to Unit Converter and press pressure.


4. Enter 5035.85 kPa and read pressure as 50.36 Bar.

5. Goto Unit Converter-> Temperature

6. Enter 282.4 K and read 9.25 C.


7. Thus at 55Bar and 15 C, ethylene should be

supercritical!

8. Mahesh explained to Sujay and his team that at those

conditions ethylene is supercritical and hence the

observation by operators is correct.


Situation 4

HOD Mahesh was called by the Business Division head Anil at

a customer site in Europe about a complaint. The customer-

Laura complained that your liquid propylene you claim to be

99.997 % pure with balance being ethylene. However, when I

analysed the gas on top of this liquid propylene with a GC, it

had 0.19 % ethylene in it. That means your propylene is only

100-0.19 = 99.8 % pure. You are making a fool out of me and

I donot want your propylene! I will stop taking your product!


Anil and Mahesh were at customer site in Europe under

tremendous stress and started analysing the problem.

Being Chemical Engineers, they knew that gas composition

need not be the same as liquid composition of propylene.

The relationship between liquid composition and gas

composition is governed by Raoults Law. Yi x Pt = Xi x PiSat .

To determine Yi, they would need Pisat.

1. Goto Process Calculator - > Component Properties ->

Vapour Pressure.

2. Select Ethylene from drop down list and enter

temperature as 20 C (lab Analysis temp).


3. Read Vapor Pressure as 63.08 Bar.

4. Since the GC gas is 1 Bara, Pt = 1 Bara.

5. Xi = (100-99.997)/100 = 3 E -5.

6. Hence yi = 3 e-5 x 63.08 / 1 *100 = 0.189 %.

7. Hence Lauras GC anaylsis is correct and this is all making

sense.

8. Ethylene being more volatile, concentrates in gas phase.

9. To correctly analyse this liquid, Laura should have

vaporized the liquid phase and analysed the gas. Not

taken the gas over this liquid and analysed it.


10. Laura was convinced and she accepted the

product!

Situation 5

Chairman Kuldeep called Anil and Mahesh to his cabin.

Kuldeep observed that engineering analysis is very slow in

this company. If engineers cannot think fast, how will

decisions be taken in this company and how will we move

ahead at reasonable speed?


Kuldeep explained to Anil and Mahesh that engineers should

have models in their heads about the processes they are

working on. They should know the process inside –out with

all the numbers. Please ask all process engineers to prepare

like this.

However Anil and Mahesh observed that making models

about our processes is very expensive. ASPEN costs 20,000

USD per year !

Kuldeep explained that a piece of paper, engineers brain,

data and calculator should be enough for this. Please find

data and a calculator. For the more complex processes we

can use ASPEN.

Anil and Mahesh found data and calculations in “Process

Calculator” at


https://itunes.apple.com/us/app/process-

calculator/id730928677?is=1&mt=8

and

https://play.google.com/store/apps/details?id=sai.processcalculator

These are mobile apps on Iphone and android and can be

easily downloaded on engineers smart phones.

This would improve the engineering analysis speed of

engineer and Kuldeep was happy with this.

https://itunes.apple.com/us/app/process-calculator/id730928677?is=1&mt=8

https://itunes.apple.com/us/app/process-calculator/id730928677?is=1&mt=8

https://play.google.com/store/apps/details?id=sai.processcalculator

03-process calculator use illustration

Documents