DH -- Environmental Improvements in an&NA Production

8/3/2019 DH -- Environmental Improvements in an&NA Production

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CASE STUDY:

ENVIRONMENTAL IMPROVEMENTS IN NA&AN PRODUCTION

Nitrogen Fertilizer Production

Technology Workshop 2011, Seville

Puertollano Factory: Ammonia Plant, NA Plants and Ammonia Storage

David Herrero Fuentes


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Fertiberia

N

Puertollano

Location of the Factory

Introduction AN mistNH3 slip in NA-2


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Birds eye view of the facilities

1. Ammonia Plant2. Nitric Acid Plants

3. Ammonia Storage Tank

4. Ammonia Loading Station

5. Ammonium Nitrate Plant

6. Nitrate Storage Area

7. Urea Plant

8. Urea Storage Area

9. Bagging plant

10. Water tank C. I.

11. Central Offices

12. General Workshop

13. Warehouse



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Configuration and main figures

AMMONIA

PLANT

600 tpd

NITRIC

ACID

PLANTS

440 tpd

UREA

PLANT

400 tpd

AMMONIUMNITRATES

PLANT

700 tpd

NH3

CO2

LOADING

NH3

HNO3

NH3 TANKS

10.000 t

HNO3 TANKS

1.800 t

BULK STORAGE

25.000 t

Urea prill

UAN PLANT

600 tpd

ANS TANK

100 t

LOADINGA

REA

BULK STORAGE

55.000 t

AN prill

ANS

olution

Urea

Sol.

N.GAS

ELECT.

N2

Sale

WATER

AIR

NAT2.000 t

Dolomite&

Additives



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IPPC Permit

Plant Description Dust(mg/Nm3)

NH3(ppm)

Nox(mg/Nm3)

N2O(ppm)

NH3 Reforming, Aux.Boiler, Desulphuration,

Methanation, Synthesis

5 200 (C)

HNO3-1 Flue-gas 5 5(C) 200(C) 800(C)

HNO3-2 Flue-gas 5 5(C) 150(C) 300(C)

AN Prilling Tower

Dolomite grinding&transport

40

10

40

Urea Prilling Tower

Synthesis

35 20

50

Loading Bulk loading

Bagging

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5

Emissions: Maximum values, main parameters

(C) : Continuous measurement. For non-continuous measurements, monthly.

* Immission in the perimeter of the factory to be lower than 75 g/m3

Waste water disposal to water body: Maximum values, main parameters, continuous measurement

Description Volume Total Nitrogen (mg N/l) pH T(C)

Centralized waste water

treatment system

2.880 m3/d < 25 6-9 < 25



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NOx SCR (Shell-CRI)

Nitric Acid Production and De-NOx system

Introduction NH3 slip in NA-2

Catalytic

Combustion

Air

NH3

NO oxidation&

NO2 absorptionNOx

NH3

NOx:

2000-4000 ppmv

V2O5

Energy

NA-2 basic diagram (M/M plant)Puertollano FactoryTost

ack

NOx:

< 150 mg/Nm3

H2

O

HNO3

380-400 tpd

Air

6NO + 4NH3 5N2 + 6H2O

6NO2 + 8NH3 7N2 + 12H2O

NO + NO2 + 2NH3 2N2 + 3H2O

4NO`+ O2 + 4NH3 4N2 + 6H2OReactions

NOx SCR transforms NOx and added NH3 into nitrogen and

water .

NH3 slip from the reactor depends on inlet NOx level, desired

outlet NOx level and on the efficiency of the system.

BAT references in Europe define a maximum emission of 5

ppmv with a NOx emission lower than 150 mg/Nm3.

AN mist


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Follow-up of Ammonia slip in NA plantsPuertollano Factory. 5s measure, daily average

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

18/06/2010 09/07/2010 30/07/2010 20/08/2010 10/09/2010 01/10/2010 22/10/2010 12/11/2010 03/12/2010

Date

NH3slip(ppmv)

NA-2 NA-1

NH3 slip in NA-2 was 7 times higher than best references

BAT: 5 ppmv

Average: 34 ppmv

Introduction NH3 slip in NA-2 AN mist


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Potential causes for increasing ammonia slip

Excess ammonia (only temporal)

Poor mixing of flue-gas and ammonia before the De-

NOx reactor

Deviated-from-design operating conditions (pressure,

temperature)

End of catalyst life cycle.

Bypass of the catalytic bed.



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Preliminary Analysis

The De-NOx system was totally replaced in 2000 by CRI, worldwide reference. CRI came

several times to the plant and analyzed the causes together with Fertiberia:

Cause Analysis Decision

Poor mixing NH3 injection&mixing system was also replaced in 2000 under CRI

specification and supervision, using well-proven SULZER static mixers.

To be checked in

next turnaround

Deviations

from the

design

conditions

Parameter

Flow (Nm

3

/h)Inlet temperature (C)

Pressure (bar.a)

Inlet NOx concentration (ppm)

Design

< 50.000>220

>3,5

< 4.000

Current

< 50.000220

3,7

< 4.000

OK

Catalyst life

cycle

Catalyst is 10 years old. Estimated life cycle by the vendor is 20 years. In

2009 catalyst was checked and 25 kg (2,1%) were added due to

settlement. Samples were taken and analyzed by the vendor, showing

good activity levels.

OK

Bypass of the

catalytic bed

The internal module (squared) is placed on a plate. The plate is

supported on a ring and sealed with manganese-containing fiberglass

joints. Theses joints are fixed in place just by gravity forces and pressure

differential.

Calculation showed that only a 0,9% of gas bypass will produce an 40

ppmv increase of the ammonia slip!

To be checked in

next turnaround



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Lateral flow reactor description

Detail of the lateral-flow module:

Installation of upper

sealing plates:



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Reactor

wall

Supporting

ring

Supporting

plate

Original

joint

Detail of the union between

supporting plate and reactor wall:

In 2009 turnaround, actions were taken to avoid gas bypasses

Added in

2009

Mdule

(catalyst)

NOx+NH3

Perforated

plate

After 2009 turnaround, ammonia slip decreased from

40 to 20 ppmv. At the end of the next gauze

campaign emission reached 40 ppmv again.



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If you can not beat them

500 lts of catalyst were purchased

previously to 2010 turnaround.

It was planned to cover all the lateral

areas outside the module and exposed

to rich NOx gas with a catalyst layer.

Thus, if any bypass, NH3 and NOx would

react in the presence of catalyst,cleaning the bypass gas and avoiding

tail gas contamination with NH3/NOx

Replace

ImproveCatalyst



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December 2010 turnaround: Inspection of the NH3 injection&mixing

Ammonia injections:

Checked, OK

Static mixers:

Checked, OK



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Inspection of the catalyst module

Height and distribution of the catalyst:

Module is opened. Catalyst in good

condition. Maximum settlement of 3 cm in

some areas without gas bypass. Somecatalyst is added. Joints are replaced. Upper

sealing plates reinstalled.

Checked, OK

Channels sealing:

After visual inspection, no leaks.

Checked, OK



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Through the end of the cover plate

visual inspection shows no joint at all.

Joint is replaced and additional jointas planned is added, with special

care.

A new cover plate is installed, thistime with some overlapping.

Gas bypass is confirmed



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and catalyst is added in the lateral areas between reactor and module



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Follow-up of ammonia slip in NA-2

Puertollano Factory. 5s measure, daily average

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

18/06 09/07 30/07 20/08 10/09 01/10 22/10 12/11 03/12 24/12 14/01 04/02 25/02 18/03 08/04 29/04 20/05 10/06

Date

NH3slip(ppmv)

Results: better than expected, permanent almost zero emission

Average: 34 ppmv

Average: 0,4 ppmv

2010 2011

BAT: 5 ppmv



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New challenges

To reduce the number and intensity of ammonia slip or

NOx excursions: Optimization of the control system.

To reduce ammonia consumption in the De-NOx based

on plant condition and legal limit (operate the plant

closer to the limit).

Installation of an advanced process control systemin the De-NOX unit of NA-2



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The challenge: reduction of AN mist from the AN prilling tower

February 9th, 2011 16:00 hrs - Soluble AN34,5% fabrication However, when producing

LDAN this problem does not exist. The only difference: prilling temperature



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All-purpose prilling tower

ANS consumption by product%. Year 2010. Total=166.028 t AN 100%

Soluble

AN34,5

CAN27AN33,5

LDAN

UAN32

ANS20

Hot ANS

33%

21%

3%

19%

15%

6%

2%

Prilling time distribution%. Year 2010. Total= 6.516 hours

Soluble

AN34,5

40%

25%

CAN27

AN33,5

4%

LDAN

31%

During more than 65% of the yearly operating time of the prilling tower, corresponding to 187days, mist generation is observed (AN34,5/CAN27/AN33,5). More than 55% of the ANS is

transformed into these prilled fertilizers.



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Simplified diagram of the prilling unit

Final concentration Additives mixing Prilling&Gas Treatment

Falling-film evaporator

by hot air&steam

Inlet: 90-94% AN

(with/without additives)

Outlet: 96-99,8% AN

Mixing tank for:

- Dolomite

- Dust from screens&mill

- Additives

8 single-stage scrubbers, 2 of them

treating both prill ing tower exhaust and

air from the final evaporator.



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Mist effect does not imply failure to comply with environmental permit

Though complying with legal limits, Fertiberia has the concern to solve out this mist

problem. Mist is generated in descending order in the following products: Soluble AN,

AN33,5 and CAN27. When prilling LDAN no mist is observed.

Emission measures are consistent with visual observation of the mist generation.

Dolomite is well washed out by the scrubbers

Ammonia emission also depends on an adequate control of ph and flow in the washing liquor.

Emission Legal Limit

(mg/Nm3)

Number of

measures (06-10)

Average

(mg/Nm3)

% over

the limit

Ammonia 40 67 28 4,5

Dust 40 300 14 1,0

Ammonia Dust

Measures

(Number)

Average

(mg/Nm3)

% Over

the Limit

Measures

(Number)

Average

(mg/Nm3)

% Over

the Limit

Sol.AN 20 29 10,0 79 25 2,5

CAN27 15 32 6,7 83 17 1,2

LDAN 32 21 0,0 138 6 0,0

Product

Emission



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Mist generation mechanism: liquid AN vapor pressure

1. Ammonia and nitrous fumes evolve from the

liquid surface of the prill in the vicinity of the

prilling bucket. Gas release depends on the vapor

pressure of the AN at the surface of the prill.

Vapor pressure depends on the state and

temperature of the AN.

2. As gases cool down when finding cooler air, they

combine and crystallize to form AN sub-micron

crystals.

3. These crystals, due to low weight, are sucked up

by the fans. The mesh of the scrubbers is not

design to retain sub-micron particles, so crystals

are emitted, being the origin of the mist

(persistent blue-grey typical emission).

4. Gas stream from final evaporator is combined

with exhaust gases from the prilling tower before

entering the scrubbers, worsening the problem

(same mechanism)

State T(C) VP(mmHg)

Solid

38 0,015

111 0,037

129 0,126

143 0,289

160 0,958

Liquid

170 1,400

180 2,510

190 3,690

200 6,310

210 9,050

AN Vapour Pressure



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Public references

Mist size

Ref.

Size distribution, % weigth

(particle diameter, m)

12

CAN27

(no gas

treatment)

83% 8% 1% 8%

Ref.

Size distribution, % weigth

(particle diameter, m)3

TAN 10% 40% 25% 25%

Mist: 86,2%

Mist: 68,8%

When searching for references, it was confirmed

that mist is generated by sub-micron emission.

Scrubbing system at Puertollano is not designed to

deal with those particle sizes.

Scrubbers designed for mist elimination are not an

option in the case of Puertollano, due to CAN27

operation.



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Size distribution investigation at Puertollano (in course)

0%

25%

50%

75%

100%

0 5 10 15 20

%Weigt

h

m


Total emission by product*

* Measured in 1 out of 8 scrubbers, 4 periods of 1 hour per port, 2

ports per scrubber. Total measuring time: 8 hours per product.

Average values.

Estimated size distribution curves

Mist

Soluble AN34,5 (prilling+final concentration)

LDAN (priling + final concentration)

LDAN (only prilling)

Mist in LDAN < 25% of emission

Mist in Sol.AN34,5 > 90% of emission


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Actions in study/course/implemented

When preparing the ANS to prill:

Replace AS reactor by AS crystal after the final evaporation.

Add a desiccant (eg.magnesium sulphate) to ANS for reducing

prilling&concentration temperature while not modifying quality properties.

When prilling:

Test water sprays in the vicinity of the prilling bucket to reduce vapor pressure byfreezing prill surface.

When treating the exhaust gases:

Increase air flow (and thus the cooling rate), by refurbishing fan scrubbers.

Segregate final concentration and prilling exhaust gases. Install a dedicated

treatment system for final concentration gases.

Launch study with main engineering companies to modify/refurbish/replace the

scrubbing system by other to tackle with sub-micron emissions, taking into

consideration the presence of dolomite when prilling CAN27.

Priority

1


Installatio

n&

OperationCosts

Prio

rity

2

Prio

rity

3


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Public references: water sprays



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Public references: desiccant addition

Prilling tower for CAN27 (no treatment). Addition of magnesium sulphate reduced mist generation, by

reducing operation temperature (final concentration outlet) from 175-180C to 155-160C



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Public references: scrubber modification

TAN prilling tower. Vertical filters for sub-micron particles were added to the scrubber.



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Is it possible to solve mist emission in a multipurpouse prilling tower?

WHY NOT?

THANK YOU!, ANY IDEAS?


Documents

DH -- Environmental Improvements in an&NA Production