The variable frequency drive controlling the CO2 compressor motor at an IFFCO fertilizer plant was causing problems by shutting off during faults and not allowing individual control of motor speed. Modifications were made to allow faults to be diagnosed, run the motor individually without other equipment, and reduce motor speed to match compressor needs. This eliminated issues like backups and saved over Rs. 10 lacs annually in energy costs while improving plant output. The implemented suggestions received awards and recognition for the employee.

1. Modification in CO2
Compressor Drive of Carbon
Di-Oxide Recovery Plant
Satyajeet S. Naib
Asst. Manager (Electrical)
IFFCO Phulpur Unit

2. Contents…
1. Introduction
2. Problem Faced
3. Suggested Solutions
4. Implemented Suggestion
5. Tangible Benefits

3. Introduction
IFFCO Phulpur Unit Phase-II has a Carbon Di-Oxide
recovery unit installed in 2006 based on the proprietary
KS1 solution.
This provides auxiliary supply of CO2 to boost the urea
production in the plant.
To maintain/control the CO2 header pressure we have a
Variable Frequency Drive controlled Motorized CO2
compressor.
It was commissioned by Boldrocchi in 2007 and uses a
ABB make ACS800 160kW Variable Frequency Drive.

4. Variable frequency drive

5. Total Problems Faced…
Loss of huge
anount of enegy
Inconvenience
to operator
Need to use
antisurge
valve
Loss of
Rs 10lac
per year
Reduction of Plant
Load by 10 %No Indication
of Faults
Backfeed of discharge
due to low suction
No Provision to
run motor
individually
No control of speed to
the operator

6. Problem Faced
The Fascia Unit turns off if any
kind of fault occurs leaving no
trace of what happened
The Motor was found burnt 4
times since 2011 due to
overheating and cost of
rewinding is Rs 2.5 Lacs with a
downtime of 2 months with a
reduction of 10% plant capacity

7. Problem Faced
The Drive used to cut off it own power
in case of any fault

8. Problem faced…
This Variable Frequency Drive was operated in a fixed mode although it
could support both Direct Torque Control & Scalar Modes
It used to maintain the speed of the Motorized Compressor at a fixed value
of 2650 RPM.

9. Problem faced…
This motor runs along with a sequence of motors & burners which
run the Incinerator system for burning off the waste/used KS1
solution.
Due the problems in the Yokogawa based DCS system there was
no provision to run this motor individually.
When we have to run this motor alone, all the other motors along
with the RLNG fired burner in the Incinerator also run.
This caused a loss of Rs.5,00,000 in electricity charges and
Rs.4,90,000 as cot of RLNG.
There was a need to provide a way to run this motor alone without
all the other motors and burners in the sequence.

10. Problem Faced
 The motor used is rated at 3000 RPM but the requirement of compressor is only 2250
RPM, but the Drive used to reduce speed only to 2650 rpm.
 Thus we had to back feed the discharge of the compressor to its suction to maintain its
suction pressure.
 There was no provision to control the speed of the motor via DCS.
 This caused a daily energy loss of more than 15000 rupees.
Anti Surge
Valve
CO2
Compressor
CO2 Header
Urea Plant 1 Urea Plant 2

11. Possible
KillChallenge
Implement
Suggested Solutions…
BIG
Payoff
SMALL
Payoff
EASY
to implement
HARD
to implement

12. Implemented Solution Part 1
1 NO contact of
R1 was removed
from here
Now only
emergency
button can cut
input supply
to drive
Now there will a very
clear indication of
fault

13. Implemented Solution Part 2…
 Power (Mechanical) ∝ Speed x Torque
 PowerElectrical = (PowerMechanical) / (Efficiency of Motor)
 This means that if the motor is operating at half the speed and producing
full torque, the motor is outputting half of its rated power.

14. Implemented Solution Part 3…
Anti Surge
Valve
CO2
Compressor
CO2 Header
Urea Plant 1
Urea Plant 2
 The drive control was given to an operator via DCS so that the speed of the motor can be reduced
to about 2250 RPM. This was not possible earlier due to faulty wiring.
 Due to this the anti-surge valve was totally off loaded and back feeding of discharge was no longer
necessary.
 A provision was also made to run this motor without the whole sequence which caused additional
savings.

15. Tangible Benefits…
 Based on the aforementioned solutions we
achieved the following:
 Speed reduction of approx 400 RPM &
need of Anti-surging has been eliminated
 Savings of Rs. 10 lacs yearly in energy &
gas by not running the whole sequence
along with the drive.
 Input power reduction of 37% of the
rated 160kW.
 Energy savings of 60 kWH per hour.
 Considering the cost of power generated
in IFFCO Phulpur Unit i.e. 10.5 Rs/kWH
this results in a daily energy saving of Rs.
15,120

16. Tangible benefits….
Cost of Rewinding -semi annually Rs. 5,00,000
Cost of Variable frequency drive Rs. 20,42,000
Cost of Motor Rs. 13,00,000
Energy Savings if Motor runs 330
days a year
(64x11x24x330)+10,00,000
Rs. 59,89,600
Total Recrring Savings Rs. 59,89,600
Toral Savings in 2014-15 Rs. 1,00,00,600
Considering that the motor runs 24 hours a day for 330 days a year.
Cost of production for 1 Kwh of power in Amm-2 is 10.5 Rs/Kwh

17. Rewards & Recognition…
 This suggestion after implementation in
August 2014 has received the following
awards.
 This suggestion has been awarded 2nd
Prize at the INSSAN Creativity meet
at IFFCO Phulpur Plant along with
cash prize of Rs.2500
 This Suggestion has also been awarded
a merit award at IFFCO Inter-Unit
Creativity Meet at Delhi in June-2015
 For this suggestion, I have been
awarded as the most creative
Employee of IFFCO Phulpur and a
cash Prize of Rs. 10,000.