Modification in CO2 Compressor Drive of Carbon

Di-Oxide Recovery PlantSatyajeet S. Naib

Asst. Manager (Electrical)

IFFCO Phulpur Unit

Contents…1. Introduction2. Problem Faced3. Suggested Solutions4. Implemented Suggestion5. Tangible Benefits

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.

Variable frequency drive

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

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

Problem Faced

The Drive used to cut off it own power in case of any fault

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.

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.

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

PossibleKillChallenge

Implement

Suggested Solutions…BIGPayoff

SMALLPayoff

EASYto implement

HARDto implement

Modification in the design of the control circuit and modification in DCS.

Change in source of control supply and change of Drive interface.

Change Motor Drive Set completely- Costing 35 Lacs

Implemented Solution Part 11 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

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.

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.

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

Tangible benefits….

Cost of Rewinding -semi annually Rs. 5,00,000Cost 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

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.