NOx SOx CO2 and Urea Dust Control inFertilizers Plants.pdf

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NOx, SOx, CO 2 and Urea Dust Control in Fertilizers Plants
Presentation · February 2024
DOI: 10.13140/RG.2.2.17498.93122
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NOx, SOx, CO2 and Urea Dust
Control in Fertilizers Plants
By
Prem Baboo
Fellow of Intuition of Engineers
Retired from National Fertilizers Ltd, India
&
Dangote Fertilizers Ltd, Lagos, Nigeria
Introduction
NOx, SOx & CO2 emission are the serious
problem in any fertilizers plant. The urea
production and use of nitrogen fertilizers lead
to the release of SOx, CO2, N2O and CH4,
which are among the most important global
GHGs. The synthesis of ammonia, from which
all synthetic fertilizers are produced, accounts
alone for about 0.8% of the global GHG
emissions and 2% of global energy.
CO2 emission factor from urea is 0.2 kg
Carbon per kg urea, which is equivalent to the
mass percent of Carbon in urea. Urea dust
control system should be there in every plant.
The pollution point of view urea dust is very
harmful to buildings and humans. If you
install CO2 recovery system, then you can also
control SOx and NOx. In reality dust emission
control system should be installed in prilling
tower. It is not costly; slightly per ton of urea
energy will increase but it is necessary for all
urea plants. Number of Revamp Companies
are available in market.
Key words
Dust emission, Prilling tower, Pollution,
environment. SOx, NOx, CO2 Emission,
Environment.
Urea Dust Control in Prilling Tower
Case-1, when Urea dust emission from
prilling tower top is between 60 to 100
mg/Nm3
In this case no major modification is
required only you can change the bucket
from smaller to slightly higher prills size as
per below table.
DETAIL SIEVE ANALYSIS, UREA PRILLING TOWER
BUCKET No.
SIMCO
BUCKET (SB-
275)Indian)
TUTTLE
BUCKET (TX
434)(USA)
Summary
Sr.
No.
Sieve (size
distribution)
Sample Sample Simco Tuttle Size
Prills % Prills % SB 275
TX
434
Detail
1 .+2.8 1.67 3.08 1.67 3.08 OVERSIZE
2 -2.8+2.36 6.43 5.42
96.64 95.37
NORMAL
SIZE
3 -2.36+2.00 16.48 17.11
4 -2.00+1.70 28.1 30.4
5 -1.70+1.40 28.47 31.02

www.researchgate.net 22nd
Jan. 2024
2
6 -1.40+1.18 13.42 8.69
7 -1.18+1.00 3.74 2.73
8 -1.00+0.80 0.83 1.1
1.69 1.55
UNDER
SIZE
9 -0.85 0.86 0.45
Total 100 100 100 100
Table-Prills Size Distribution
Different type of Prilling bucket are
available in market, e.g. Tuttle bucket
(USA) and Simco Bucket (Indian) you can
order and they will provide within month as
per you’re your requirements such as
summer bucket, winter bucket etc.
Fig-1, Sampling of Prilling Tower dust

Jan. 2024
3
Fig-2, Prilling Bucket
Case -2, Urea dust emission from prilling tower is between 100-140 mg /Nm3
Then Vibro priller can be installed if
temperature of prills goes to higher(e.g-60-
650
C) then CFD (Cooling Fluidized dryer) and
BFC (Bulk flow cooler) along with dust
recovery system. can be installed to cooled
down prilles temperature. The dust emission of
prilling tower can be controlled by vibro priller.
You can install Vibro priller with replacement
of existing prilling Bucket or Prilling
distributers. Prilles quality improved with
Vibro priller because the dust emission will be
minimum.it has wide capacity range and simple
in design. Environment friendship.95% normal
size and minimum dust emission. Average
prills size 2-4 mm and cooling of prilles in
summer season.Detail as shown in the figure-
The Vibro priller can be installed from Russian
Company NIIK.
Fig-3. Vibro Priller

4
Fig-4, CFD
Fig-5, BFC
Case -3, If the Dust emission from Prilling
Tower is between 140-160 mg/Nm3
Then dust recovery system from Prilling
Tower bottom can be installed.as per
following figure. Urea dust recovery system
in prilling comprising conducting the prilling
operation in a co-current stream of air (moving
downward with the solidifying prills through
the prilling tower) and then collecting the prills
and substantially all by-product urea dust
(fines) at the bottom of the tower. some of the
smaller particles are entrained in the cooling air
stream and are carried out the top of the tower,
where they are vented to the atmosphere and
lost. this 1oss to be a minimum of 2-3 ton/day
for fertilizer prills(as per plant capacity)
Because of the smaller average product particle
size, counter current air flow in the prilling
tower during the production of prills must be
limited to natural draft. The use of forced draft
as used in the production of fertilizer prills
would result in excessive dust losses about 150-
250 mg/Nm3, while in natural prilling tower
this value is 60-90 mg/Nm3 after
implementation of this dust recovery from
bottom of the prilling tower it is reduced to 30-
50 mg/Nm3. Reduced air flow (natural draft),
however, introduces a problem of its own.
Because of insufficient prill cooling during
periods of high production or of high ambient
temperature in summer season, formations of
urea are deposited on the walls and on the
bottom collecting cone of the prilling tower.
This formation is very dangerous can be
removed shutdown to shut down. Following
advantages
1. Dust losses at the top of the pril tower
can be reduced
2. Product build-up on the walls of the
prill tower during the production of
smaller size can be reduced
3. Heat and fumes at the top of the priliing
tower can be controlled for
environments
4.

Jan. 2024
5
Fig-6, Dust recovery from PT bottom
Case-4, If the Dust emission from
Prilling Tower is between 160-200
mg/Nm3
In this case Urea dust recovery system can be
installed in top of the prilling tower. For
recovery of the dust from prilling tower top two
number of steel duct are provided. There is a
possibility to place the equipment on the ground
level but it is less efficient with regard to both,
investment and operation. As shown in the
Figure-
The urea solution is used for scrubbing the urea
dust. Dil H2SO4 and Dil HNO3 are also used to
recover dust and ammonia.
For installing de dusting system following
aspects should be considered:
1. Gas flow through prilling towers
2. Dust and ammonia content in mg/Nm3
3. The temperature of gas. Ambient
temperature maximum and minimum
4. Whether only urea dust or urea dust
and ammonia is to be removed, and in
case the emission of both pollutants
should be controlled, whether they are
to be recovered as one or two separate
streams.
Following equipment’s are required for
de dusting system
1. Scrubber SS 304 L
2. Blower with motor 3.3 KV
3. Urea solution recycle pump
4. Filter
5. Condensate tank
6. Additives H2SO4 or HNO3
7. Condensate/DM water
The particulate matter and ammonia and Urea
reduced by scrubber installed at bottom floor,
we can say natural prilling Tower convert into
force prilling Tower by installing following
(i) Duct from PT to Ground
floor. (duct size according
to plant load, may be 2000
X 3000 mm)
(ii) One number Blower high
capacity.
(iii) Scrubber with two recirculation
pump one is for H2SO4 and one
is for urea solution pump
(circulation plus transfer to
Vacuum section or Urea tank,
when conc. Reached 20-30%)
(iv) SS duct of min 2 mm THK.
(v) One high power motor
about 2-3 MW.
After Treatment the ammonia /Urea, Ammonia-
10-20 ppm and Urea 15-30 mg/Nm3

Jan. 2024
6
Fig-7, Dust recovery from PT top
Fig-8

7
Fig-9, Dust Recovery from PT top
Control of CO2 in Reformer Flue
gases
Flue gas CO2 recovery plant utilizes the
hindered amine solvent process is based on a
proven and most advanced technology for the
recovery of CO2 from flue gases of various
conditions. The user of this process will enjoy
such benefits as low energy consumption, low
solvent degradation, and lower corrosively.
CO2 is recovered from Natural gas fired boiler
and steam reformer flue gas, compressed and
used for urea production for Fertilizer
Industries.CO2 recovery capacity 400-600
metric T/D. Flue gas is cooled and SOx is
removed before entering CO2 absorber.CO2 is
captured with amines with improved KM CDR
Process. The Carbon Dioxide Recovery
technology and license is provided by
Mitsubishi Heavy Industries of Japan and the
unit will have a capacity of 450 MT Per Day of
CO2.
The most positive benefit to the Environment is
the Carbon dioxide required for this process
that will be recovered from the presently vented
Reformer flue gases, resulting in annual
reduction in Green House Gases. The
modification of the existing facility will include
the construction of the flue gas duct connecting
the CO2 recovery plant to the existing stack.
The flue gas will be extracted from the stack
and brought to the CO2 recovery plant by the
Flue gas blower which is installed downstream
of Flue gas quencher. The modification of the
existing facility will include the construction of
the flue gas duct connecting the CO2 recovery
plant to the existing stack. The flue gas will be
extracted from the stack and brought to the CO2
recovery plant by the Flue gas blower which is
installed downstream of Flue gas quencher.
CO2 RECOVERY PLANT

8
The CO2 recovery sections consist of four
main sections;
1. Flue gas quenching section.
2. CO2 recovery sections.
3. Solvent regeneration section.
4. CO2 compression section
Flue gas quenching section
Flue gas quencher shall be the cylindrical
column using structure packing. The
temperature of flue gas is too high to feed CO2
absorber. Lower flue gas temperature is
preferred for the exothermic reaction of CO2
absorptions and solvent consumptions. Hot flue
gas, therefore, shall be cooled in flue gas
quencher by direct contact with circulation
water supplied from top of flue gas quencher
prior to CO2 absorber. The circulated water is
cooled by Flue gas cooling water cooler.
CO2 Recovery Section
CO2 absorber is the cylindrical column
structure packing. CO2 absorber has two main
sections, the CO2 absorption section in the
lower part and the treated flue gas washing
sections in the upper part.
CO2 Absorption Section
The cooled flue gas from Flue gas quencher is
introduced into bottom section of CO2
absorber. The flue gas moves upward through
the packing, while the CO2 lean solvent is
supplied from the top of the absorption of the
absorption section onto the packing. The flue
gas contacts with the solvent on the surface of
the packing, where CO2 n the flue gas is
absorbed by the solvent. Te rich solvent from
the bottom of CO2 absorber is sent to
Regenerator by rich Solution pump through
heat exchanger. The Chemical reactions which
take place between carbon dioxide and an
aqueous MEA solution generally represented as
follows;
2(HOCH2CH2NH2) +CO2 +H2O =
(HOCH2CH2NH3)2CO3…………….….. (1)
HOCH2CH2NH2+CO2+H2O =
HOCH2CH2NH3HCO3…………….……. (2)
Carbon dioxide can also react directly with
MEA to form a carbamate according to the
reaction:
2(HOCH2CH2NH2) + CO2 =
2CH2NHCOONH3CH2 ……………….…(3)
Water Wash Section
The flue gas from the CO2 section absorption
section moves upward into the treated gas water
wash section in the upper part of CO2 absorber.
The treated gas is washed by the water
containing the solvent as well as to be cooled
down to maintain water balance within the
system. The water wash section is the
combination of the packing and several
demisters. One special demister is included in
their demisters, which s developed by MHI.
The system configuration is MHI’s proprietary
design and already commercialized in the
several plants. The treated gas shall be
exhausted from the top section of CO2
absorber.
Solvent Regeneration Section
Regenerators shall be the cylindrical column
using structure packing, where the rich solvent
is steam-striped and CO2 is removed from the
rich solvent. The rich solvent from the bottom
of CO2 absorber shall be heated by the lean
solvent from the bottom of Regenerator in
Solution heat exchanger. The heated rich
solvent shall be introduced into the upper
section of Regenerator, where it contacts with
the stripping steam. The rich solvent shall be
steam-stripped in Regenerator, and regenerated
to the lean solvent. The steam in Regenerator
shall be produced by regenerator reboiler,
which uses LP steam to boil the lean solvent.
The overhead vapor shall be cooled to 400C by
Regenerator condenser. The partially
condensed water shall be returned from
Regenerator reflux drum to the top of
Regenerator by Regenerator reflux pump. The
lean solvent shall be cooled to the optimum
reaction temperature by solution heat

9
exchanger and lean solution cooler prior to
being sent to the CO2 absorber.
2CH2NHCOONH3CH2 =
2(HOCH2CH2NH2) + CO2 (Product)
10% of the lean solvent flows through Carbon
filter to remove oil and soluble impurities.
Guard filters are provided before and after
Carbon filter to remove insoluble particulate.
CO2 Compression Section
The product CO2 gas shall be compressed by
CO2 compressor through Compressor suction
scrubber to maintain product CO2 pressure as
0.8kg/cm2g at CO2 recovery plant battery limit
and cooled to 400C by the Compressor
discharge cooler. Then, product CO2 shall be
sent to the existing Urea plant by
interconnection with existing CO2 header or by
any other product.
Solvent Reclaiming (Intermittent Operation)
A reclaimer unit is provided in order to
eliminate the salts. When the salt content in the
solvent is close to the maximum set limit, the
reclaimer is operated to evaporate the solvent to
return its vapor to the system, so that the salts is
concentrated to sludge to be discharged.
Incineration System
Incineration system shall be provided for
disposal of reclaimed waste from the reclaimer
an incinerator, probably a down-fired brick-
lined cylindrical furnace, shall completely
decompose the reclaimed waste liquid by
combustion. Natural gas shall be supplied to the
burner and the reclaimed waste liquid shall be
sprayed into the incinerator. The incineration
system shall be designed and constructed by the
selected vendor technology. The system shall
confirm and verified by Detailed Engineering
Contractor based on the information from the
vendor.

10
Fig-11 CDR
Control of NOx and SOx
Following technique for removing
NOx and Sox
Currently, in most industrial processes,
NOX and SOX are treated separately. Emissions
of SOX are significantly reduced and
completely removed from flue gases by a “wet
scrubbing technology,” which uses a slurry of
alkaline sorbent (usually limestone or lime), or
seawater to scrub gases. In this method, the
SO2 wet scrubbing product, calcium sulfite
(CaSO3), is further oxidized to produce
marketable gypsum (CaSO4·2H2O). This
technique is known as forced oxidation, flue gas
desulfurization (FGD), or fluidized gypsum
desulfurization.
For Nox “selective catalytic reduction” (SCR).
The reduction yield of nitrogen oxides to
nitrogen via the SCR is typically high, but this
technique is extremely expensive. Other
options include enhancing the removal
efficiency of NOX in wet scrubbers by gas-
phase oxidation of water-insoluble NO gas to
water-soluble NO2, HNO2, and HNO3. This
oxidation can be accomplished by using strong
oxidation reagents like gaseous hydrogen
peroxide (H2O2), ozone (O3), or non-thermal
plasma. The oxidized NOX species may then be
easily removed by caustic water
scrubbing. Additional advantages of this
process include the fact that both SOX and
NOX can be removed simultaneously. The
above process further comprises the step of
contacting the oxidized NOX and SOX,
dissolved in a liquid phase, with ammonia to
produce an ammonium nitrate NH4NO3 and
ammonium sulfate (NH4)2SO4 mixture, which
can be used as a nitrogen-contained fertilizer.
The drawbacks of gas-phase oxidation are
requirements of expensive reagents, corrosion-
resistant systems, and specialized safety
equipment to handle ozone and hydrogen
peroxide safely. These additional requirements
increase the cost of operations significantly.

11
The activated carbon tests with synthetic flue
gas containing SOx only, NOx only and the
mixtures of SOx and NOx at elevated pressures
and ambient temperatures showed that
activated carbon is able to remove SOx and
NOx when fed individually or together.
Removal of SO2 and NO from flue gas by wet
scrubbing using an aqueous Sodium Chlorite
(NaClO2) solution.
scrubbing with aqueous acidic solutions
containing hydrogen peroxide to oxidize NOx
and SO2 in HNO3 and H2SO4.
Conclusion
High prill temperature due to ambient
conditions also will enhance the dust emission
the cleaning of the louvers is required at this
condition. The adjustment of the bottom and top
louvers of the prill tower is important as per
plant operation and weather conditions. dusting
system at the top of the prill tower and it is in
continuous operation. When there is flow
restriction near the nozzles and air path, a
shutdown of the de-dusting system is taken.
Nozzles, air path and sump are cleaned and the
de-dusting system is put back in operation.
prilling device obtains substantially
monodispersed droplets under creation a
relative quiescent zone near the showerheads,
the solidifying time as the key parameter in
determining the size of prilling unit needed. The
existing prilling tower revamp task is difficult
but not impossible. It is necessary for legally
environment law and regulation according to
world standard. An important consideration in
prilling tower design is the selection of suitable
criteria against which the adequacy of the
design results can be tested. A number of such
criteria suggest themselves. About 0.01 G cal
/ton of energy will be increased for prilling
tower revamp because the 3.3 KV motors are
required for large capacity blowers.
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