R-1 LP R-2 1

NFL NANGAL & BATHINDAUrea Plant

Presented ByPrem Baboo

Sr. Manager(Prod)

National Fertilizers Ltd, India

R-1 LP R-2 2

Urea Processes used in NFL units

NANGAL: Technimont Total Recycle

Process.

BATHINDA & PANIPAT: Mitsu toatsu C

Improved Process.

VIJAIPUR: Snamprogetti ammonia stripping

process.

R-1 LP R-2 3

NANGAL UREA PROCESS

BRIEF DESCRIPTION :

It is a Montedison total recycle process.

Plant is installed in April,1978.

Plant capacity is 1450 Te/day.

Commercial production after revamping started on

Feb 1st,2001.

Before revamping its capacity was 1000 Te/day.

R-1 LP R-2 4

Plant Description

CO2 Compressor & H.P.Pumps

Urea synthesis.

Urea separation.

Recovery section.

Vacuum section.

Prilling section.

Waste water section.

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Specification Sheet

Ammonia at B/L

NH3 99.5% by weight

Water 0.5% by weight

Carbon Dioxide at B/L

CO2 98.99% (Vol.)

H2 0.6 to 1.5% (Vol.)

CH4 0.1 to 0.15% (Vol.)

H2S 0.65 ppm (Vol.)

CH3OH 6.00 ppm (Vol.) for old compressor

CH3OH 1000 ppm (Vol.) for new compressor

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Specific Consumption

Ammonia 0.574Te/Te of urea

Carbon dioxide 0.745 Te/Te of urea

Steam 30ata 1.23 Te/Te of urea

Power 135 kwh

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CO2 Compressor

There are two motor driven reciprocating compressors

Old Compressor

No. of Stages 3

Capacity 17510 Nm3/hr.

Suction/Discharge press. 11/220 Kg

RPM 300

Motor Power 2250KW

Oxygen content maintained 2200ppm

R-1 LP R-2 8

NEW COMPRESSOR:

No. of Stages 4

Capacity 9500 Nm3/hr.

Suction/Discharge press. 1.5/220 Kg

RPM 350

Motor Power 2400KW

Oxygen content 3500ppm

R-1 LP R-2 9

Ammonia feed pumps

There are three reciprocating plunger pumps

Make Peroni

No. of plungers 5

Pulsation dampener nil

Capacity 53NM3/hr. each

Suction pressure. 30Kg/cm2

Discharge pressure 220 Kg/cm2

R-1 LP R-2 10

Ammonia feed pump

One no. ammonia pump (New) having less

capacity 25NM3/hr.

Two ammonia pumps run at 100% load.

Ammonia is directly taken from ammonia

plant at 30 kg & fed to reactors at

220kg.Before feeding to reactors it is pre

heated up to 80°C.

R-1 LP R-2 11

Carbamate feed pumps

There are four reciprocating plunger pumps

Make Peroni

No. of plungers 5 in old & 3 in new

Pulsation dampener only in new pump

Capacity 53M3/hr. each

Suction pressure. 70Kg/cm2

Discharge pressure 220 Kg/cm2

Three pump run at 100% load.

R-1 LP R-2 12

Urea Synthesis

Urea reactor {Old}

Volume 50M3

No. of trays 14

Type of trays High eff. Casale trays.

Temp. Bott./Top 184/196OC

Pressure 220Kg/cm2

Liner SS 316 L

Thickness 12mm

R-1 LP R-2 13

Urea Synthesis

Urea reactor {New}

Volume 33M3

No. of trays 9

Type of trays High eff. Casale trays.

Temp. Bott./Top 184/198OC

Pressure 220Kg/cm2

Liner 2RE69

Thickness 6mm

R-1 LP R-2 14

New Reactor

Fresh ammonia & carbon dioxide are fed to mixer, then to carbamate condenser, where ammonium carbamate is formed. Heat of reaction is taken out in the form of 6 .0 atasteam generation. The hot carbamate flows to reactor R-2 where residence time is enough to get 69% conversion.It is once through reactor, no carbamate solution is fed to it.

R-1 LP R-2 15

Old Reactor

The rest of CO2 & NH3 are fed to old

reactor. All the carbamate sol. of the plant

fed to old reactor.

Both reactor outlet joins & pr. Is controlled

by PRC-1 at 220kg.

R-1 LP R-2 16

Reactor feeds

The expected best operating condition are:

New sec. Old sec.

Capacity (TPD) 600 1050

Pr. (ata) 220 220

Temp. (ºc) 196 196

N/C 2.9 2.75

H/C 0 0.7

Conversion (%) 69 55

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Conventional Process

Decomposition:

NH4COONH2 +Heat = 2NH3 + CO2

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Urea Separation.

1st stage Pressure 70 Kg/cm2

Temperature 185OC

Urea conc. 54.5%

2nd stage Pressure 12 Kg/cm2

Temperature 150OC

Urea conc. 65%

3rd stage Pressure 3 Kg/cm2

Temperature 130OC

Urea conc. 72%

R-1 LP R-2 19

Recovery Section

Pressure 1.5 Kg/cm2

Temperature 125OC

Outlet conditions

NH3 0.04%

Urea 1.0%

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Vacuum Section

1st stage vacuum system Pressure 0.35 ata

Temperature 128OC

Urea conc. 95%

2nd stage vacuum system Pressure 0.04 ata

Temperature 138OC

Urea conc. 99.6%

R-1 LP R-2 21

Prilling Section

Tower

Height 104.5mtr

Free fall ht. 80mtr

Diameter 22mtr

Air flow 8,00,000 nm3/hr

Urea in emission 40mg/nm3.

Scrapper type conical

Bucket

Make Tuttle/Simco

Number TX-267, 268 & 130

R-1 LP R-2 22

Product Quality

Total Nitrogen 46.5%

Moisture 0.35%

Biuret 0.8-0.9%

Mean prill dia 1.75mm

Sieve analysis

Over size nil

Proper size 98.5%

Under size 1.5%

R-1 LP R-2 23

Waste Water Section

Feed at 100% load 35m3/hr

Feed water analysis

NH3 3.00%

UREA 1.2%

Hydrolyser pr. 20Kg/cm2

Hydrolyser temp. 1980C

R-1 LP R-2 24

Waste Water Section

Distillation tower

Pressure top 4.5Kg/cm2

Pressure bottom 5.5 Kg/cm2

No. of trays 33+12

Outlet water analysis

NH3 40 ppm

Urea 35 ppm

R-1 LP R-2 27

Plant Start up

Reactor is filled with dilute solution.

In case of empty reactor, it is to be filled with

start up solution.

In case of cold start up, reactor solution is

first heated up to 125 OC .

First stage{70ata} remain by passed.

R-1 LP R-2 28

Plant is started in once through operation.

Once through operation means the solution is

send to urea solution tank and Carbamate is

send to start up solution tank from 2nd stage.

Ammonia feed to reactor and pressure is

maintained at 150ata for 5 minutes and then

CO2 is send to reactor.

Plant Start up

R-1 LP R-2 29

Reactor pressure will increase according to the

temperature and feed ratio.

As the temperature and pressure reaches to the

desired condition then the Carbamate from 2nd stage

is diverted to the 1st stage.

As the level of 1st stage condenser increases, start

the Carbamate pump and feed Carbamate to the

reactor.{known as total recycle}.

Plant Start up

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After total recycle, temperature and pressure

of each stage are maintained.

The urea solution is sent to vacuum section.

After normalizing vacuum section, melt urea

diverted towards bucket.

Plant Start up

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Objective of revamping

Optimum utilization of ammonia plant capacity.

Increase in urea plant capacity by 450 MTPD.

Improvement in urea prills quality.

Reduction in specific energy consumption for urea

from 10.26 G cal. To 9.4G cal. Per MT of urea.

Reduction in dust emission.

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Revamping

Project Cost; Rs.161Crores

Project executed by; M/s. Urea Casale

Switzerland.

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Major equipment added:

CO2 compressor.

NH3 pump.

Carbamate pump.

Urea reactor.

Methanol scrubber.

Urea melt pump

New vacuum distiller {HE9}

R-1 LP R-2 34

Additional vacuum condenser.

New circular Prilling tower.

High efficiency trays in old urea reactor.

Major equipment added:

R-1 LP R-2 36

Urea Quality After Revamping

Over size reduced to nil.

Temperature in summer reduced from 90OC

to 55OC.

Crushing strength increases from 350

gm/prill to 650 gm/ prill.

Urea dust emission reduced . Now it is

< 50mg/nm³.

R-1 LP R-2

Urea casale’s high efficiency tray

R-1 LP R-2