1. BRIEF USE ILLUSTRATION OF PROCESS
CALCULATOR
BY KULDEEP VARMA
MAY 5, 2015
CTAC
S5a/a, Plot 14, Chinmay Colony, Karvenagar, Pune 411052.

2. Page 1 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?

3. Page 2 of 14 – Kuldeep Varma. PROCESS CALCULATOR.
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. Page 3 of 14 – Kuldeep Varma. PROCESS CALCULATOR.
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!

5. Page 4 of 14 – Kuldeep Varma. PROCESS CALCULATOR.
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.

6. Page 5 of 14 – Kuldeep Varma. PROCESS CALCULATOR.
Solution with Process Calculator
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.)

7. Page 6 of 14 – Kuldeep Varma. PROCESS CALCULATOR.
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.

8. Page 7 of 14 – Kuldeep Varma. PROCESS CALCULATOR.
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?
Solution with Process Calculator
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.

9. Page 8 of 14 – Kuldeep Varma. PROCESS CALCULATOR.
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.

10. Page 9 of 14 – Kuldeep Varma. PROCESS CALCULATOR.
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.

11. Page 10 of 14 – Kuldeep Varma. PROCESS CALCULATOR.
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.

12. Page 11 of 14 – Kuldeep Varma. PROCESS CALCULATOR.
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!
Solution with Process Calculator
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).

13. Page 12 of 14 – Kuldeep Varma. PROCESS CALCULATOR.
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.

14. Page 13 of 14 – Kuldeep Varma. PROCESS CALCULATOR.
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?
Solution with Process Calculator
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

15. Page 14 of 14 – Kuldeep Varma. PROCESS CALCULATOR.
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.