1

MINISTRY OF EDUCATION AND TRAINING
HANOI UNIVERSITY OF MINING AND GEOLOGY

PHAM DINH THANH

GRADUATION
THESIS
INTRODUCTION OF THE NITROGEN PRODUCTION
TECHNOLOGY IN CA MAU FERTILIZER PLANT AND
CALCULATION OF THE HEAT TRANSFER AREA OF THE
CONDENSER


2

HANOI – 06/2019


3

ACKNOWLEDGEMENT
First of all, I would like to deeply express my sincere gratitude to my
supervisor, Dr. Vu Van Toan for his invaluable guidances, suggestions, and
assistances throughout this thesis. Without his guidance, supports, especially his
meaningful feedback, this thesis cannot complete on time.
Secondly, I also thank the Oil Refining and Petrochemical Department, Oil and
gas Faculty, Hanoi University of Mining and Geology for not only the tremendous
academic support, but also giving me a lot of career opportunities, scholarships for
exchanging with the universities in the world. And thank you to all lecturers who

had assisted me during my studying time in Advanced Program
Last of all, I wish to express my sincere gratitude to my family, friends for their
encouragement and moral support. They are the most important people in my life
and I dedicate this thesis for them.
Sincerely

Pham Dinh Thanh


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TABLE OF CONTENTS


5


6

LIST OF THE TABLES
Table 2.1. The market share of PVCFC
Table 2.2. The miles stones of PVCFC
Table 2.3. The main products in PVCFC
Table 2.4. The target of the demineralized water
Table 2.5. The targets of compressed air
Table 2.6. The properties of nitrogen and oxygen
Table 2.7. The standard output air


7


BFW:

LIST OF ABBREVIATIONS
Boiling Feed Water

CCR:

Central Control Room

LMTD: Log Mean Temperature Difference
PVCFC: Petro Vietnam Ca Mau Fertilizer joint stock Company
PFHE:

Plate-Fin Heat Exchanger

PIC:

Pressure Indicator Control


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INTRODUCTION
Motivation of the thesis
During the past decades, Vietnam has transformed to low middle income
country from one of the poorest countries. Vietnam now is one of the most dynamic
country in ASEAN. Vietnam is also an agricultural power in the world with a total
volume of agricultural exports of more than 40 billion dollars and 15 th in the world.
Vietnamese agricultural products are exported to 180 countries and territories [1].

Therefore, the demand of the fertilizer is very big in agriculture.
Fertilizer is an important factor contributing to increased productivity and
quality of agricultural products. It helps the agricultural products to get international
standards. In the production of fertilizers, nitrogen (N 2) is an important component
in the ammonia synthesis segment. High purity N 2 production is an essential
requirement not only to provide purity N2 for the fertilizer industry but also to other
industries such as stainless steels production and semiconductor manufacturing.
Liquid nitrogen storage is very important in the fertilizer production plant,
which contributes to ensuring the supply of vapor nitrogen helps the plant operate
stably. Nitrogen is stored in liquid form, so calculating and designing the condenser
is a very necessary problem to liquify the vapor nitrogen.
For the practical problems, it was decided to choose the thesis “Introduction of
the nitrogen production technology in Ca Mau fertilizer plant and calculation of the
heat transfer area of the condenser”.
The objective of the thesis
In this thesis, it was focused on to make the readers realize more detail about N 2
production technology, how its effects to overall economy and especially in the
fertilizer industry. Besides, this study provides a clear understanding of the factors
make the change of purity N2 in distillation tower.
The structure of the thesis
As the motivation of the thesis, it was divided into 3 parts as below.
Chapter 1: Overview of nitrogen
Chapter 2: The technology to produce nitrogen gas in Petro Vietnam Ca Mau
fertilizer joint stock company (PVCFC)
Chapter 3: Calculation of the heat transfer area of the condenser to get 32 l/h
liquid nitrogen in PVCFC


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CHAPTER 1: OVERVIEW OF NITROGEN
1.1 Introduction of nitrogen
Nitrogen is a chemical element with symbol N and atomic number is 7. At room
temperature, it is a colorless, odorless, tasteless, inert gas and exists in the form of
N2 molecule. Nitrogen accounts for about 78% of the Earth's atmosphere and is part
of every living organism. Nitrogen can create many important compounds such as
amino acids, ammonia, nitric acid and cyanide. The stable chemical bonds between
nitrogen atoms make it difficult for both organism and industry to convert N 2 to
useful chemical compounds, but also release a large amount of useful energy when
burning, blasting or decomposing back into nitrogen gas. Nitrogen is present in all
living organisms, in the form of amino-acids (DNA and RNA). The human body
contains about 3% nitrogen by weight, which is the fourth most common element in
the body after oxygen, carbon and hydrogen. The nitrogen cycle describes the
movement of this element from the air into the biosphere and organic compounds,
then returns to the air.
The physical property of nitrogen at 1 atm, 0 o C (Table 1.1)
Table 1.1. The property of nitrogen [2]
Molecular formula
Molecular weight
Melting point
Boiling point
Density

N2
28 g/mol
63.15 K
77.36 K
1.25 g/L

1.2 The production and application of nitrogen in the industry

1.2.1 The production of nitrogen
Nitrogen is an industrial gas produced by fractional distillation of liquid air. After
removing CO2 and steam. The air was liquefied under the high pressure and low
temperature. The temperature was then gradually decreased to -196 o C, the nitrogen
boils and separates from oxygen because oxygen has a higher boiling temperature (183 o C). Nitrogen gas is circulated in steel cylinders, compressed under 150 atm.
In the laboratory, we create the small amount of pure liquid nitrogen by heating
slightly the saturated ammonium nitrite solution:
NH4NO2 → N2 + 2H2O
We can replace ammonium nitrite by saturated solution of sodium nitrite salt
and ammonium chloride:
NH4Cl + NaNO2 → N2 + NaCl + 2H2O


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1.2.2 The application of nitrogen
Nitrogen gas is produced by evaporating nitrogen liquid. It widely has the
application in the life and especially replace the air in some cases to avoid the
oxidation.
- Preserve the fresh food by adding pure nitrogen inside to avoid the activity of
bacteria
- Put it on the top of the liquid explosive for safety
- Manufacture the electronic components
- In manufacture of stainless steel
- Inflate the car tires, aircraft tires, reducing the problem caused by moisture
and oxygen in the air
Nitrogen liquid has low temperature so it is very useful in maintaining the
temperature
- Keep the low temperature for transporting the food
- Preserving body parts as well as sperm and egg cells, samples and probiotics

- Study about the cooling agents
- In dermatology to remove ugly malignant skin lesions or carcinogenic
potential
- Liquid nitrogen can be used as a cooling source to speed CPU, GPU, or other
types of hardware
1.3 The production technology of nitrogen in the industry
1.3.1 Deep cooling method for producing nitrogen
In the industry, some processes need a large amount of pure oxygen and
nitrogen. It is collected after liquefying air and then distillate it to have nitrogen and
oxygen, separately [1]. Besides, we will obtain Kr, Ne, etc.
- Pure oxygen with 95-97% oxygen is used in the chemical industry and
metallurgy
- Pure oxygen with 99.5% oxygen is used in the welding and medical
- Liquid oxygen is used in the missile rocket engineering
- Pure nitrogen with 99.998% N2 used in synthesizing ammonia
The cooling process have three types
Normal cooling that use water or air to cool a system from high
temperature to normal temperature. This is a self-destructive process that does not
consume effort.


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Freezing cooling that use to decrease the system from normal temperature to
-1000 o C in cold like liquid ammonia. This is a mandatory and using the force.
Deep cooling that use to decrease the temperature under -1000 o C (using
nitrogen liquid).
To produce the raw gas material for the synthesis process ammonia. We need N 2
and H2.
At steady state, t = 0 o C, p= 1 atm

Liquefied temperature to (N2) = -195.8 o C
Liquefied temperature to (H2) = -252.78 o C
If we want to liquefy the air to distillate, we need to decrease t o gas < to
liquefied.
1.3.2 The theory of this process
The low temperature receiving method
Throttling method
Throttling process is the decreasing pressure process of gas mixture, in the
adiabatic condition, no work and irreversible.
The pressure of gas is decreased to liquefied temperature when the change of
∆Q = 0, A=0 and irreversible (A is the work, ∆Q is the change of temperature).
The characteristic of this process: Decrease the pressure in condition the
enthalpy doesn’t change H1=H2.
For ideal gas, after throttling process the temperature doesn’t change
For normal gas: Because the existence of intermolecular forces and interactions
between molecules. Therefore, αH can increase, decrease, equal 0 and T 2 can differ
or equal T1. And so, this throttling process is more efficiently, we need to find out
the condition αH >0 (α is the relative volatility).
The decreasing pressure method to create work.
It is the process of decompressing the gas mixture under adiabatic thermal
conditions, create work and is the reversible process.
P2 reduce to P1 when the change of Q = 0, A # 0, reversible
The characteristic of this process is when we decrease the pressure, the entropy
doesn’t change.
Liquefaction cycle


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It is the cycle that happening at the cryogenic distillation tower to separate N 2

and O2 by liquefying N2 when it is separated from N2, O2 mixture. In this cycle,
there are 2 distillation towers with the pressure is about 6 atm, 1.5 atm (high
pressure column with P=6 atm, low pressure column with P=1.5 atm).
Purifying the air
For any air separation plant, it also contains 3 steps
- Purifying the air
-

Do the liquefaction cycle

-

Distillate the air into N2, O2

The others composition of the air
- The concentration of C2H2 depend on the place from 0.001- 0.1 ppm
-

The humidity depends on the season

-

Dust 0.02-0.2 g/m3

We need to remove all of it because it can abrade the valve, create dry ice, ice in
the pipe when we decrease the deep temperature, combine with O 2 to form the
explosion compound.
Remove dust
Filter equipment are metal rings impregnated with oil. When the air pass, the
dust will be remained (almost composition of the air in the table 1.2 are removed).

Table 1.2. The value of elements in the air
Composition
N2
Ar
O2 CO2 H2 He
Kr
Ne O3 C2H2 H2O
s
%V
78.09 0.93 20.95 0.03 5.10- 5.10- 18.10- 1.105

To hl (o C)
To solid (o C)

-196 -186 -183
-78

4

4

-252 -269 -153

6

-246
-83.6

0


Remove H2O
The humidity of the air depends on temperature, pressure and places (Table 1.3)
Table 1.3. The value of humidity at difference T
ToC
40
30
20

The humidity g/cm3
50.91
30.21
17.22

ToC
-10
-20
-30

The humidity g/cm3
2.31
1.01
0.44


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10
0

9.30

4.89

-40
-50

0.117
0.038

The procedure to adsorb H2O
- Use Silica gel SiO2.H2O: Silica gel is created by dehydrating gel- hydrate
acid silica with diameter 3-7 mm. The humidity of the air is 0.03 g/m 3 with to
= -52 o C.
- Use activated alumina: It contains 92% Al 2O3.H2O, and the other
composition SiO2, Na2O, FeO. After drying, the humidity < 0.05 g/m 3, to=
-63 o C.
To regenerate the adsorbent, we use hot N2 gas at the condition below:
Table 1.4. The temperature for adsorbents
Adsorbent
To regenerate

SiO2.H2O

Al2O3.H2O

167-177 o C

247-267 o C

Use zeolite synthesis: is aluminosilicate of kali, sodium at crystal form. Use
zeolite can remove CO2, H2O, C2H2, so we can design the equipment more

small
- Freezing method: Use high-capacity chains, to separate air according to the
cycle of pressure and cooling
Theory: Using cooling principle, to freeze reduces the saturated vapor pressure
of water
Firstly, we use N2, O2 waste which cooling to temperature t o = 5-7 (o C) to
separate H2O, then cooled with evaporated liquid ammonium to lower the
temperature to= -38-> -43 o C. We usually use 2 liquid ammonium chillers to work
alternately after a few hours: 1 cooling, 1 heating to melt ice.
For devices with high productivity. To produce nitrogen and oxygen, the amount
of water is frozen from the air in regenerating devices.
At to= 273 K, the air is dehumidified on the surface of the regeneration device,
in the form of condensate vapor.
At to= 240 K, cold water is changed to ice
In fact, the freezing method and the method of using adsorbents both reduce the
moisture content of water vapor in the air by physical method.
Remove CO2
-


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Similar to water, at normal pressure t o C solid CO2 = -78 o C. In the condition of
liquid air separation at to= -185 o C, CO2 will change to solid that clog the pipe and
equipment. If the system works at high pressure, it causes the explosion, burning
that is reason why we need to remove CO2.
Use NaOH solution
In the huge chain, we use the CO2 washing tower that can water NaOH solution
to the surface. And the reaction equation is
2NaOH + CO2 -> Na2CO3 + H2O

Use the freezing method
In regeneration equipments, CO2 is condensed to stay on the cold buffer surface,
when air flow is through the buffer. Then solid CO2 is removed from the buffer
surface by the reverse flow N2 and O2 during the heating phase of regeneration
equipment.
To clean CO2, we use 2 the regeneration equipments that work in the cycle. The
concentration of CO2 in the air is 15-20 cm3 CO2/ m3 air.
The CO2 remain:
Partially dissolved in liquid air at the bottom of the lower distillation column
Partly in the form of solid particles in liquid air, it can seal the throttle and disk
holes of the distillation tower, so it must filter the liquid air from the bottom of the
lower tower, before saving on the upper tower, with porous porcelain. or copper
sponge, by powder metallurgy method.
Nowadays, people have replaced the regenerative equipment in the form of a
ribbed plate, making it more economical, due to its high density, compact because
of its large surface from 50-200 m2/m3 to 1000-1300 m2/m3 or 2000-4000 m2/m3.
Remove C2H2
C2H2 gas accumulates in an explosive air separation system, because the partial
pressure of C2H2 is small, can’t be separated from air through heat exchangers.
The solubility of C2H2 is 5cm3/L liquid CO2, so quickly saturating the solid in
the solid, when the impact is volatile, mixes with O2 to cause the explosion.
The separation of C2H2 is done by adsorbing with silica gel on the way when
transferring liquid air from the bottom of the bottom tower or from the liquid air
flow to the turbine generator.
1.3.3 The separation of the air to produce O2, N2


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The smallest work for air separation is determined by the isothermal

compression of each element from the partial pressure to the mixed pressure.
L min= m*R*T*Pn*ln1/P n
With Pn is the partial pressure of n (atm)
R is gas constant 1.987 kcal/kmol* K, 8.314 kJ/k mol* K
T is the temperature of the compression process K
m is the total molecular
The minimum capacity to separate the air contain 20.9% O 2 and 79.1% N2 at
290 K is,
Lmin= -8.314*290*(0.209*ln1/0.209+ 0.791*ln1/0.791)
= -1230 kJ/mol or -1230:24.5= -50 (kJ/m3)
Choose the pressure for the distillation process
Because the difference of liquefaction temperature of N 2 and O2 is small at the
same pressure. And so, the best way to separate the air is the distillation. At each
temperature, lower pressure will bring the big difference between liquid and gas
composition. We can conclude that, for lower pressure, we can separate the product
more purity.
1.3.4 The distillation towers
It contains 1 low distillation tower at P=1.5 atm, 1 high distillation tower at P=
6-7 atm, 1 condensing equipment to connect towers.
Process: The compressed air enters the bottom of the lower tower, boiling the
oxygen-rich liquid air (35-40%) and throttle to P= 6-7 (atm) by throttling valve. At
the lower distillation tower, the evaporated N2 is condensed at the top of the tower
and it will boil liquid oxygen at the bottom of the high tower. At the high tower, we
will contain gas N2 and gas O2.
Some problem in the distillation process:
Pressure problem: P at the high tower depends on the resistance of the ducts, it
usually is 1.3-1.5 atm.
P at the low tower = 6-7 atm so that N 2 gas can boil the liquid oxygen at the
high tower
The difference between TN2 gas and TO2 liquid = 3-50 (o C) (at the low pressure,

N2 has lower boiling point than O2)
Concentration product problems: The presence of 0.932% Ar in the air affects
the process of distillation (the purity of the product). It is accumulated on the plates


16

of the upper tower. We can take argon at the plate which have the highest
concentration to distillate Argon out of the N2, O2 compound that we can get the
pure N2 and O2 (O2 ≥94%, N2≥ 98%).
Separating the inert gas from air: The distribution of inert gas in the air depends
on its boiling temperature.
Ne and He have the lowest boiling point, so it is on the top of the evaporative
condensing device (see in the Table 1.3)
Argon have the boiling point between the boiling point of nitrogen and oxygen.
And so, it is accumulated at the middle of the high tower toO2< toAr Kr and Xe with the highest boiling point will condense in liquid oxygen in the
bottom of the upper tower.
Ar, Kr, Xenon usually have the application in the industry (Ar is used in the
welding, cutting, metallurgy industry, lighting, Kr and Xe have the heat
conductivity is 2, 3 times less than that of argon, it should be used as a light filler).
All the elements of the air are shown in the table 1.5.
Table 1.5. The properties of air composition [3]
Compositio
n

Molar
weight

Density

(kg/m)

Ar
Heli
Ne
Kr
Xe
O2
N2

39.95
4.0026
20.183
83.8
131.3

1.66
0.166
0.838
3.71
5.85

Boiling
point (o
C)
-186
-269
-246
-153
-108

-183
-196

Melting
point (o
C)
-189
-271
-248
-156
-111

Critical
constants
(to)
150.72
5.201
44.45
210.55
289.75

Critical
constants
(P)
4.864
0.2275
2.721
5.424
5.82

It is taken that the fraction containing argon is not the disk with the maximum
concentration, which is lower than some of the plates, because at that time the
concentration of N2 decreases too much. (Ar 5-12%, O2 87-92%, N2 0.5-1%).
We take the Xe and Kr (0.1-0.2%) mixture in the air from the bottom of the high
distillation tower that contains 5 cm3/m3.
Technical oxygen contains 0.1-0.2% Kr-Xe, 1-2%N2+Ar, 98-99% O 2 is passed
to Kr enrichment equipment and we will get 80-95% Kr+Xe.


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1.4 Demand for nitrogen in Vietnam
Vietnam is a developing country with the need to use products made from very
large nitrogen for agriculture, heavy industry, food......Currently, nitrogen is mainly
produced in the petrochemical refineries, steel and metallurgical plants for on-site
service. In addition, there are many factories specializing in the production of
liquefied petroleum gas in Vietnam such as AirLiquide Vietnam that produced in
Bac Ninh province, Ho Chi Minh City and Ba Ria-Vung Tau province in Vietnam
and Messer at the Hai Phong city, Air product company. Due to increasing demand,
the expansion of production is essential for factories to meet the Vietnam market.


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CHAPTER 2: NITROGEN PRODUCTION TECHNOLOGY IN PVCFC
2.1 Overview of PVCFC
2.1.1 History and development of PVCFC
Petro Vietnam Ca Mau Fertilizer Join Stock Company (PVCFC), a member of
Vietnam Oil & Gas Group – Petro Vietnam (PVN) was established on March 9,
2011. The duty and responsibility of PVCFC is to manage and operate Ca Mau

Fertilizer Plant, located in Khanh An Gas – Power – Fertilizer complex, U Minh
district, Ca Mau province. [4]
The major business of PVCFC is fertilizer products.
Vision: to become the leading enterprise in Vietnam and the region in the sector
of producing and trading fertilizer and chemicals serving agriculture and oil and gas
industry.
Mission: to be a manufacture of and trader in fertilizer on petrochemical basis
serving agriculture, provide nutrition solutions to plants contributing to changing
the agriculture sector to sustainable and environmentally friendly development,
ensuring harmonious benefits for owner, customer, worker and enterprise.
Core values: “Solicitous – Friendly – Professional – Creative – Responsible –
Harmonious”.
Ca Mau Fertilizer trademark has been consistently preferred by the major
markets. Furthermore, it aimed to be continuously extended not only domestically
but also internationally.
Market share: Table 2.1 is the market share of PVCFC products
Table 2.1. The market share of PVCFC
Area
West Southern
East Southern
Cambodia
Others

2013
45%
19%
30%
4%

2014

55%
25%
35%
5%

2015
58%
22%
36%
9%

These are the milestones of PVCFC:
Table 2.2. The miles stones of PVCFC [5]
Year
2008

-

Milestones
Ca Mau Fertilizer Plant was officially started construction
Over 800,000 tons/year operational capacity
900 billion USD total initial investment capital

2016
58%
24%
38%
12%

19

2011

Establishment of PVCFC as a member of PVN
Nearly 3,200 trillion of VNC for charter capital
Nearly 800 cadres and employees
2012
Launch the product branded “Dam Ca Mau – Gold Season Seed”
500,000 tons of output after 10 months of operation
2013
PVCFC received big awards “Viet Gold Star”, “Representative
Agriculture Product”
- 1 million tons after 15 months of operation
2014 - PVCFC was selected typical M&A business for 2014 – 2015
- PVCFC received the award “National Brand”
- 128,951,300 shares were sold out
- 1,580 trillion of VND for total shares value
2015 - PVCFC was officially converted to the model of joint stock company and
listed on the HCMC Stock Exchange with stock code DCM
- Launch the high-grade fertilizer line N.HUMATE+TE with outstanding
properties
- Dam Ca Mau products were officially distributed in Cambodia market
- 3 million tons after 4 years of operation
2016 - Launch the high-grade fertilizer line N46.PLUS and N46.NANO C+
- 4 million tons after 5 years of operation
2017 - PVCFC received big awards “Vietnam Top 500 Businesses”, “Vietnam
High Quality Goods”, “Business for Employees”
- Establishment of Research and Development Center
- Complex Fertilizer Plant was officially started construction

- PVCFC was certificated “Excellent Operating Unit” by Handor-Topsoe
Denmark – Ammonia Authorized Technology Provider of PVCFC
Overview of PVCFC
There are 4 main Units in PVCFC:
1. Ammonia unit
2. Urea unit
3. Utility unit
4. Production – Bagging unit
The overall process of PVCFC:
-


20

Figure 2.1. The production diagram in PVCFC
The layout of plant is shown in the figure 2.2

Figure 2.2. The layout of plant

The products of PVCFC are listed in the table 2.3
Table 2.3. The main products in PVCFC
Group
Urea
fertilizer

Product
Granular urea

Parameter
- (N): 46.3% MIN

- Biuret: 0.99% MAX
- Moisture: 0.5%
MAX

N46.PLUS

- (N): 46% MIN
- NBPT: 230 ppm

Outstanding properties
- Fertilizer saving
- Slow decomposition
- Easy distribution and mixing,
low biuret
- High adaptability
- High productivity
- Environmentally friendly


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N46.NANO C+

Complex
fertilizers

DAP

Potassium

NPK

Bio
mineral
fertilizers

N-HUMATE
+TE

N-HUMATE
+TE 28 – 5

NHUMATE+TE
28 – 7

MIN
- DCD: 950 ppm MIN
- Biuret: 0.99% MAX
- (N): 46% MIN
- Biuret: 1% MAX
- Chitosan: 3.5%

- (N): 18% MIN
- Humidity: 0.5%
MAX
- 46% MIN
- 61% (1%)
- 46% MIN
- Humidity: 2% MAX
- (N): 16% MIN

- 16% MIN
- 8% MIN
- (S): 13% MIN
- TE: Zn, Bo
(1000ppm)
- (N): 35% MIN
- Humic acid: 7%
- Zn: 1000ppm
- B: 400ppm
- Humidity: 4%
- Organic: 9%
- (N): 28% MIN
- Humidity: 4%
- Humic acid: 5%
MIN
- Zn: 1000ppm MIN
- B: 400ppm MIN
- Organic: 6% MIN
- (N): 28% MIN
- Humidity: 4%
- Humic acid: 7%
MIN
- Zn: 1000ppm MIN
- B: 400ppm MIN
- Organic: 9% MIN

- Easy mixing, low biuret
- High productivity
- Enhance micronutrients
- Soil improvement

- Anti – pest
- Organic poison, alum, salt
resistance
- Strong growth of root
- High productivity
- Used for manuring and
dressing
- High strength and stability
- High quality and
productivity
- High adaptability
- High strength
- Soil improvement
- High quality and
productivity
- Strong growth of root
- Fertilizer saving
- High quality and
productivity
- Strong growth of root
- Soil improvement
- Strong growth of root
- High absorption
- High quality and
productivity
- Enhance soil fertility
- Stimulate beneficial
organisms
- Strong growth of root
- High absorption

- High quality and
productivity
- Enhance soil fertility
- Stimulate beneficial
organisms
- Fertilizer saving


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Ammonia unit
Ammonia production of Haldor-Topsoe SA–Denmark technology is utilized in
ammonia unit of PVCFC is shown in the figure 2.3. This is the prestige manufacture
in the field of the ammonia production which is always updated and improved.
Therefore, Haldor-Topsoe technology copyright is highly appreciated all over the
world due to its low power consumption and high efficiency.
Overall process of ammonia unit:
The production of ammonia in the factory is synthesized by stream, natural gas,
process air is shown in figure 2.3

Figure 2.3. The process for producing ammonia product
Ammonia is produced from synthetized gas with a ratio of H 2/N2 of 3/1.
Synthetized gas also contains an inert gas such as Ar and CH 4 at a certainly limit.
The source of H2 is demi water and hydrocarbon gas in the air. The supply of N 2 is
the air. Besides ammonia, the unit also has another product that is CO 2, the supply
of CO2 is from hydrocarbons in natural gas. The steps required to produce ammonia
from material sources:
- Natural gas is removed sulfur in the desulfurization unit to the parts per
million.
- Desulfurized gas reacts reforming with steam and air to form a technological

gas. Major gas components are H2, N2, CO, CO2 and steam.
- Reaction equation
CnH2n + 2 + nH2O -> nCO + (2n + 1) H2O – Q (the reaction release energy)
CO + 3H2 -> CH4 + H2O - Q and CO + H2O -> CO2 + H2 + Q (the reaction gain
energy)


23

In the process of purification gas, CO is converted into CO 2. The CO2 is then
separated from the technology gas at the CO2 splitting device.
- CO and CO2 that remaining in the CO2 splitting device are converted into
CH4 in methanization equipment by reaction with H2 before synthetized gas
enters the ammonia synthesis to avoid the poisoning of the synthesis of NH 3.
CH4 is formed have a role of an inert gas in the ammonia synthesis cycle,
used catalyst is nickel-PK -7R.
- Synthetized gas is compressed and fed into ammonia synthesis tower to
produce ammonia by this equation:
N2 + 3H2 -> 2NH3 (T = 450-500 o C, 20-25 MPa, catalyst Fe3O4 + Al2O3 + K2O)
To limit the Ar and CH4 accumulation in the synthesis cycle, a small gas stream
is extracted from the cycle. Liquid ammonia products release inert gas and
dissolved gases before being transported through urea and storage tanks.
Urea unit
There are 2 technologies used in urea unit of PVCFC:
- Urea production technology of SnamProgetti – Italy, uses NH 3 self –
dissociating based on basis of the regenerative evaporation process. With
regular updates, Snam Progeti is designed to enhance automation and safety
in high pressure and explosive environments.
- Granulation technology of Toyo Engineering Corporation – Japan (TEC)
which is developed and operated with high capacity of 3250 tons/day. TEC is

set up to pellet with various sizes, compatibly meeting every single market
requirement. Moreover, there is a dust filter equipment used in this
technology to purify the product as well as reduce the installation cost. The
diagram to produce is shown in figure 2.4.
Overall process of urea unit:
The chemical reaction to synthesize urea solution is done by the reaction
between CO2 and NH3. The figure 2.4 show all the process for producing urea:
-


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Figure 2.4. The diagram for producing urea
Chemical reactions for the synthesis of urea. Figure 2.4 is the process to
synthesis urea solution:

Overall:
The duty of urea unit is to synthesize urea (from ammonia and carbon dioxide
from ammonia unit) then shipped to granulation unit with 2385 tons of urea liquid
(96%).
Utility unit
Utility unit is one of 3 major units of PVCFC. The main mission of this unit is
to produce steam, compressed air, instrument air, nitrogen, purified sanitary water,
demineralized water, cooling water in order to guarantee that ammonia and urea
units will be operated without any warning. Besides that, waste water treatment
system (including sanitary waste water, oily waste water and ammonia
contaminated water) and flares system are also utilized in this unit.
Demineralization unit [6]
This are the processes for producing the demineralized water is shown in this
figure 2.5. Raw water is taken to the filtered tank, cation exchanger, degasifier,

anion exchanger, precision filter to remove all cation, anion, dust with many
diameters.


25

Figure 2.5. The demineralized water production unit
The targets for the demineralized water are shown in table 2.4
Table 2.4. The target of the demineralized water
Targets

Values

Units

NH3

3

ppm

Urea

3

ppm

Ph

5-9

Conductivity

≤0.2

µS/cm

Cl¯

≤0.6

mg/l

F¯

≤0.12

mg/l

SiO2

≤0.05

ppm

Purposes:
Eliminating most of Ca2+ and Mg2+, Na+, SO42-, SO32-, HSiO3-, ... in condensate
and technological water by ion exchange process to achieve technical specifications
of demineralized water.
The filter part (S20201 A-D) consists of 2 running filters and 2 backup filters. In

case the condensed water is contaminated with water but cooled, 3 filters run, 1
break filter.
The ion elimination section of 3 lines with a capacity of 210 m3/h includes:
- Positive ion elimination: Eliminate cations Ca2+ and Mg2+, Na+ ...
- Degassing: Remove CO2 from the water source by a degassing system