There are three main methods for storing liquid ammonia: storage at ambient temperature and pressure in cylindrical vessels holding 2.5-150 tons; storage under pressure in spherical vessels holding thousands of tons; and storage at atmospheric pressure by reducing the temperature to -33°C in flat-bottomed cylindrical tanks holding over 3000 tons. Safety measures for ammonia storage include instrumentation and alarms for critical parameters like pressure, temperature, and level, as well as a flare system to safely vent excess pressure and ammonia detectors to monitor for leaks.

1. Ammonia Storage & Handling
1
AMMONIA – I
SANJAY JAIN

2. IntroductionIntroduction
Storage at ambient temperature and equivalent pressureStorage at ambient temperature and equivalent pressure in cylindrical vessels.in cylindrical vessels.
This method is used when relatively small quantitiesThis method is used when relatively small quantities (2.5 – 150 T)(2.5 – 150 T) are to beare to be
stored.stored.
Storage under pressure in spherical vessels.Storage under pressure in spherical vessels. These can be constructed at sitesThese can be constructed at sites
to hold several thousand tons of ammonia. However, very large spheres areto hold several thousand tons of ammonia. However, very large spheres are
uncommon and most vessels are in the range ofuncommon and most vessels are in the range of 500 to 3000 tons500 to 3000 tons. Refrigeration. Refrigeration
equipment may be used to lower the temperature of the ammonia and in suchequipment may be used to lower the temperature of the ammonia and in such
cases the vessels operate at lower temperature than ambient. This type ofcases the vessels operate at lower temperature than ambient. This type of
storage is often referred to as semi-pressure or semi-refrigerated.storage is often referred to as semi-pressure or semi-refrigerated.
Storage at atmospheric pressure.Storage at atmospheric pressure. Ammonia can be stored at atmosphericAmmonia can be stored at atmospheric
Pressure by reducing the temperature to –33Pressure by reducing the temperature to –3300
C. In this condition it may beC. In this condition it may be
contained in cylindrical flat bottomed tanks, since the pressure, the tank mustcontained in cylindrical flat bottomed tanks, since the pressure, the tank must
withstand, is only imposed by the head of liquid. In practice, a slight positivewithstand, is only imposed by the head of liquid. In practice, a slight positive
pressure is maintained to simplify the operation of refrigeration system. Thispressure is maintained to simplify the operation of refrigeration system. This
method of storage is generally adopted when quantitiesmethod of storage is generally adopted when quantities in excess of 3000 tonsin excess of 3000 tons
are involved. Many tanks have been built in theare involved. Many tanks have been built in the 20000 – 35000 tons20000 – 35000 tons range withrange with
few in excess of 35000 tons.few in excess of 35000 tons.
Three methods of storage of Liquid Ammonia are currently used, the choiceThree methods of storage of Liquid Ammonia are currently used, the choice
primarily depending on the quantity to be stored, economy and end use.primarily depending on the quantity to be stored, economy and end use.
2

3. Single walled tank:Single walled tank: This comprises of flat bottom tank with a dome roofThis comprises of flat bottom tank with a dome roof
designed to withstand the stated conditions. Tanks of this type will havedesigned to withstand the stated conditions. Tanks of this type will have
external surfaces insulated to minimize heat gain from the surroundings.external surfaces insulated to minimize heat gain from the surroundings.
Double wall tank:Double wall tank: The outer tank is not designed to contain any escape ofThe outer tank is not designed to contain any escape of
liquid from the inner tank, its function being only to support and protectliquid from the inner tank, its function being only to support and protect
the insulation. The simplest form comprises an inner tank which isthe insulation. The simplest form comprises an inner tank which is
surrounded by an outer tank, from the roof which is suspended ansurrounded by an outer tank, from the roof which is suspended an
insulated deck designed to fit loosely with in the shell of inner tank.insulated deck designed to fit loosely with in the shell of inner tank.
Double integrity tank:Double integrity tank: This tank consists of double wall construction withThis tank consists of double wall construction with
both tanks designed so that in the event of failure of inner shell theboth tanks designed so that in the event of failure of inner shell the
ammonia will be contained by the outer shell. The inner tank is openammonia will be contained by the outer shell. The inner tank is open
topped and the insulation be applied to the exterior of the outer tank .topped and the insulation be applied to the exterior of the outer tank .
The inter-space between the tanks will contain only cold ammonia vapor.The inter-space between the tanks will contain only cold ammonia vapor.
A suspended deck type insulation arrangement may be used as anA suspended deck type insulation arrangement may be used as an
alternative to insulate the roof.alternative to insulate the roof.
Atmospheric storage tanks:Atmospheric storage tanks:
Cylindrical flat bottom tanks, used for large storage of ammonia in fullyCylindrical flat bottom tanks, used for large storage of ammonia in fully
refrigerated condition, may be divided into three basic types.refrigerated condition, may be divided into three basic types.
3

4. Liquid ammonia is received from the ammonia plant
temp. of -330
C. When ammonia is being transferred
to the storage tanks, flash vapors are generated.
In normal operation, vapor blower K-7001 is always
running to remove ammonia vapors generated due to
ingress of heat to the storage tank & are sent to
GP-II (Ammonia refrigeration compressor system)
for condensation & liquid ammonia production; and
only at the time when vapor blower (K-7001) is in
maintenance/break down or in the event of build up
of excessive pressure, these vapors taken to the
refrigeration system (K-2001 A/B) for liquefaction
and sent back to the storage tanks
Process Description
4

5. Ammonia Vapor
from tank Ammonia Vapor
to Amm-2
From Tanks
PDIC 7001
Ammonia Blower K-7001
PV 7001
PG
PG
PV7002
5

6. PIC 512
T 2001 B
Ammonia Storage
Ammonia to
Urea
Ammonia Vapor
Flare header
HV 502 A HV 502B
Flare
From A-1
Liquid Ammonia
From A-2
Liquid Ammonia
EMV 507
EMV 506
PV 512
P-2001A P-2001B P-2001C
T 2001 A
HV 501
HIC 7001
T 2001 B
6
Loading/Unloadin
g arm

7. Flare and drain systemFlare and drain system
For disposal of vent ammonia vapor from ammonia tank andFor disposal of vent ammonia vapor from ammonia tank and
equipment safety valves (except safety valve on ammonia tank,equipment safety valves (except safety valve on ammonia tank,
which shall be vented directly to atmosphere), flare system iswhich shall be vented directly to atmosphere), flare system is
provided.provided.
Drain system is provided to drain the vessels for anyDrain system is provided to drain the vessels for any
maintenance. The liquid from drain lines from static equipmentsmaintenance. The liquid from drain lines from static equipments
are sent to vent drum where evaporated vapor ammonia from theare sent to vent drum where evaporated vapor ammonia from the
top is released to flare header.top is released to flare header.
The system consists of vent drum, flare stack, NG supply etc.The system consists of vent drum, flare stack, NG supply etc.
7

8. Flare StackFlare Stack
Flare stack height is 30 M which is designed for ground levelFlare stack height is 30 M which is designed for ground level
radiation of maximum 1200 BTU/hr/ftradiation of maximum 1200 BTU/hr/ft22
and ground leveland ground level
concentration of 25 ppm ammonia and 30 ppm maximum NOconcentration of 25 ppm ammonia and 30 ppm maximum NOXX
concentration. It consists of 2 pilot burners, one flare tip andconcentration. It consists of 2 pilot burners, one flare tip and
automatic flare front generation. Flare stack is also providedautomatic flare front generation. Flare stack is also provided
with labyrinth seal, which prevents ingress of atmospheric airwith labyrinth seal, which prevents ingress of atmospheric air
into the flare line by reversing the fluid path. Water seal isinto the flare line by reversing the fluid path. Water seal is
provided for labyrinth seal and riser pipe to drain any rain waterprovided for labyrinth seal and riser pipe to drain any rain water
that may enter.that may enter.
Natural gas is used as pilot gas.Natural gas is used as pilot gas.
Supply rate : 6 NmSupply rate : 6 Nm 33
/hr./hr.
Auto ignition temperature of ammonia: 651Auto ignition temperature of ammonia: 651 00
CC
Explosive range of ammonia: 16-25 %.Explosive range of ammonia: 16-25 %.
To minimize the hazard, a small amount of nitrogen or naturalTo minimize the hazard, a small amount of nitrogen or natural
gas is continuously purged to flare header. gas is continuously purged to flare header.
2 NH2 NH33 + 3/2 O+ 3/2 O22 -------- NN22 + 3 H+ 3 H22 OO
But there is some possibility for generating some undesirableBut there is some possibility for generating some undesirable
oxides of nitrogen.oxides of nitrogen.
8

9. 9
9

10. 250 mmWC to 2.7 Kg/cm2
g
T-2001
K-2001 A
First Stage
10

11. T-2001
K-2001 First Stage
Flash Vessel
11

12. 2.5 Kg/cm2
g to 16 kg/cm2
g.
T-2001
K-2001 First Stage
Flash Vessel K-2001 Second Stage
12

13. Condenser
13

14. Receiver
14

15. 15

16. 16

17. Flare
17

18. Ammonia Vapor
from T-2001 A/B
K-7001
PV 7002
PIC 7002
Ammonia Vapor to AMM-
II
K-2001 A/B
1 2
Saturator
V-2001
V-2002
Flash
Vessel
E-2001 A
Condenser
E-2001 B
Condenser
CW CW
CW
V-2001
Receiver
B-2001
KO
Drum
PV 509
PIC 509
LIC 504
LIC 505 LIC 506
PIC 511To Flare
Header
18

19. 19

20. 190000utershellHeight
25000 ID outer shell
23400 ID inner shell
6 mm Thick Single Tap Welded
Dome Roof
Ground Level
Bottom Insulation 200
Foam Glass bricks and
25 mm thick Sand Layer
Foundation
Poly Urethane Foam Shell
Insulation 210 mm Thick
Outer Shell Stiffener
3.6 Thick
Suspended Deck
250 Thick Fiber Glass
Deck Insulation
18000InnerShellHeight
17520MaxLiquidLevel
Storage Tank T-2001 A/B
20

21. 1 Storage capacity 2 x 5000 Tons of liquid ammonia at -330
C
temp.
2 Normal Op. pressure of tank + 350 mmWC
3 Range of operating pr. of tank +200 to +800 mmWC
4 Design pressure of tank + 1050 mmWC
5 Design vacuum of tank - 50 mmWC
6 Safety valve pr. setting + 1050 mmWC
7 Vacuum relief valve setting - 50 mmWC
8 I.D. / Height (inner shell) 23.4 M / 18.0 M
9 I.D. / Height (outer shell) 25.0 M / 19.0 M
10 Insulation Shell - PUF
Suspended Deck - Fibre Glass
Bottom - Foam Glass
Storage Tank Specifications
These storage tanks are of double wall, double integrity design (steel cup in steel
tank) and outer tank shell is designed to contain entire liquid ammonia in the event
of failure / leakage in inner tank
21

22. Ist stage: (design)
Suction : 0.96 Kg/cm2
A / -20 0
C
Discharge : 4.8 Kg/cm2
A./ 106.5 0
C
Capacity : 621 Kg/hr.
2nd stage: (design)
Suction : 4.6 Kg/cm2
A / 1.5 0
C
Discharge : 20.66 Kg/cm2
A./ 121.68 0
C
Capacity : 883 Kg/hr.
Ammonia Compressor
K-2001 A/B
Service: To compress vapor
ammonia from tank during
holding duty and unloading
from plant.
22

23. Intermediate Flash Vessel: (V-2002)
Service: To saturate the compressor
first stage discharge before
compression in second stage by
bubbling the vapors through liquid.
Liquid is taken from V-2003 and
returned to T-2001.
Operating Pressure : 3.8 Kg/cm2
g
Operating temperature : 1.5 0
C (max)
Design Pressure : 25 Kg/cm2
g
Design Temperature : - 34/60 0
C
I.D. : 700 mm
Length : 2500 mm
Material of construction :LTCS.
Insulation : PUF
23

24. Type : Vertical, Barrel, Multistage, centrifugal.
Capacity : 47 M3
/hr. (32 tons/hr)
Minimum Continuous Flow: 10 M3
/hr.
Discharge Pressure : 25.55 Kg/cm2
g
Efficiency : 56.4 %
Material (case/impeller) : LTCS
Motor (KW/rpm) : 75 / 2900
Insulation : PUF (cold)
No. of stages : 10
Ammonia Pumps P-2001 A/B/C
Service : To dispatch liquid ammonia to plant battery limits. The suction and
discharge headers of pumps are designed for a combine flow of 69 MT/hr.
The pumps can also transfer liquid ammonia from one tank to another tank
through plant ammonia unloading line.
The minimum flow to the pump suction is assured by minimum flow line. A
part of the discharge is sent to the tank via ARC (Auto Recirculation
Control) valve and minimum flow line when pump operates with discharge
valve closed condition.
24

25. Ammonia Blower K-7001
Capacity : 1719.6 Nm3
/hr.
Inlet Volume Flow: 1654.43 Nm3
/hr.
Temperature : -33 (min), -10 0
C (normal).
Pressure: 100 (suction)/ 1140 (discharge) mmWC g.
Differential Pr. : 1040 (rated) mmWC g.
Speed : 2940
Power : 9.8 KW.
MOC : case – LTCS, internals - SS
Impellers : 1,
Dia : 980 mm
Blades : 14
Driver : Induction Motor, 22 KW, 415 V, 50 Hz.
25

26. 26

27. (1) Instrumentation of high reliability have been used viz. two
independent systems for the important measurements such as tank
pressure, level and temperature.
(2) Dependable alarms and interlock system for critical parameters.
(3) Flare system availability to take care of excess pressure build up by
venting & burning ammonia vapors manually or automatically through
HV-502 A/B.
(4) Reliable safety valves to take care of any build up of pressure in the
tank beyond a pressure of +1050 mmWC.
(5) Installation of Ammonia detectors( 7 nos.) at specific locations for
detection of amm. leak in storage area.
(6) Arrangement of water spray at tank top and water curtains around
compressors house, ammonia transfer pumps & B/L I/Vs to control the
leakage of ammonia at the source.
Safety
27

28. PRESSURE / TEMP. AND LEVEL CONTROL FOR
AMMONIA STORAGE TANKS
1) PRESSURE AND TEMPERATURE CONTROL
Under normal conditions, pressure control of vapour in the tanks
is achieved through the vapour blower, which discharges the
vapour into the suction of Amm-2 refrigeration compressor
system for compression & condensation of liquid ammonia. This
operation takes care of flash vapours generated during transfer
of ammonia to the storage tanks from ammonia plant & vapours
generated as boil off.
The Vapour blower K-7001 (having rated cap. of 1320 kg/hr) has
the capacity to handle the max. vapours generation, calculated
as 1307 kg/hr considering total ammonia production @ 150
T/hr of GP-I & II is transferred at -320
C temperature when all
four streams of urea trips .
28

29. In the event of build up of excessive pressure (above +750 mmWC) due to
(1) Failure of Vapour blower/refrigeration system or,
(2) higher rate of transfer of liquid ammonia from ammonia plant- I & II
resulting in higher generation of flash vapour or,
(3) Damage to insulation resulting in higher boil off,
Venting is done to flare stack through vent control valves HV-502 A & B
(Cap.595 kg/hr each) to bring the normal pressure in the tanks and to make the
conditions safe from any untoward release of ammonia vapors in the
atmosphere.
In addition to this, two nos. 12" x 16" safety relief valves (having relieving cap.
of 25,470 kg/hr & set pressure +1050 mmWC) and four nos. 8” vacuum relief
valves (suction cap. 3763 kg/hr) have been provided on each tank. The safety
valves are designed to release ammonia vapours that may get generated due to
any external fire around the tanks. While the vacuum valves protect the tank
from vacuum due to failure of safety interlocks or reliquification system.
These safety relief valves and vacuum relief valves are mounted on three-way
valves in such a way that even if one safety/vacuum relief valve is isolated for
maintenance the other valve remain lined up with tank. 29

30. If the level in storage tank is Very High, the level high alarm and
interlock I-103 will close the control valves PV-512 on the
wagon/truck unloading line and HV-501 & HV-7001 on the liquid
ammonia transfer line from plant – I & II. Similarly, in case of Very
Low level in the tank, the level low alarm and interlock I-104 A/B will
close the respective tank outlet valves (i.e. EMV-506 / 507).
2) TANK LEVEL CONTROL
Level Measuring System:
Ø Inner Tank is provided with
- Servo type Float operated Level gauge
- Differential Pressure type Level transmitter
Ø Outer tank is provided with
- Differential Pressure type Level transmitter
30

31. Pressure/Temperature Measuring/Monitoring System:
Normally the pressure/temperature in storage tank is maintaining between 200
mmWC and 550 mmWC and -33o
C. The tanks are provided with
Ø Pressure transmitter: used for recording the pressure of the tank
Ø Pressure switches: used for compressor loading and unloading
Ø Interlocks: To trip compressor and pumps on very low tank pressure.
Ø The tanks are provided with Pressure gauge on each tank top, a common PG
at tank bottom, one pressure indicating recorder for each tank and one pressure
indicating controller are provided in control panel. Two number of multipoint
temperature recorder are provided to record liquid ammonia temperature in
storage tank and re-liquification system.
Ø Pressure relief valves and Vacuum relief valves (Three way valves): protects
the tank from over pressure and vacuum incase of failure of safety interlocks or
reliquification system. These are mounted on three way valves in such a way that
if one pressure or vacuum relief valve is isolated for maintenance the other valve
remains lined up with tank.
Ø The tank pressure can be controlled by manual venting device HIC-502 A/B.
when the tank pressure is high, the operator can manually vent vapor ammonia to
flare stack H-2001.
31

32. 1. Level alarm:
• If the level in the storage tank is very high, the level high alarm
and interlock I-103 will close the control valves PV-512 on
wagon/truck unloading line and HV-501 in the liquid unloading line
from plant.
• In case of very low level in the tank, the level low alarm and
interlock I-104 close the respective tanks out let valves.
I-104 A closes EMV-506
I-104 B closes EMV-507
If both the tanks level Is very low then both EMV-506 and EMV-507
are closed and this leads to the tripping of all the ammonia pumps.
Alarm/Interlock Logic System:
A. Storage Tanks
32

33. 2. Pressure alarm
· If the pressure in the tank is very high (805
mmWC), the pressure high alarm interlock I-102 will close
the control valves HV-501, HV-503, PV-512 and opens the
tank vents HV-502 A/B. This will lead to the closing of
liquid/vapor inlets to the tank and venting of ammonia
vapor from tank to flare.
· In case of pressure falling very low (150 mmWC),
I-101 will stop the ammonia pumps P-2001 and stops the
compressor.
33

34. I-101 stops the pump in case of very low pressure in tank.
I-105 stops the pump if both tank outlet valves are
in closed condition.
I-106 A will stop the pump P-2001 A in case of low
differential pressure across the pump
(25 Kg/cm2
g)
I-106 B will stop the pump P-2001B in case of low
differential pressure across the pump
I-106 C will stop the pump P-2001 C in case of low
differential pressure across the pump.
Interlocks - Ammonia Pumps
34

35. I-101 stops the compressor in case of very low
pressure in tank.
I-107 trips the compressor in case of high liquid level
in the ammonia saturator V-2001.
I-108 trips the compressor in case of high level in
the intermediate flash vessel V-2002.
I-109 trips the compressor in case of low cooling
water flow to the condenser E-2001 A/B.
I-111 A/B Trip respective Comp. K-2001 A/B if the First
stage suction pressure is low. (-400 mmWC)
I-112 A/B Trip respective Comp if first stage discharge
pr. Is high. (4.2 Kg/cm2
g)
I-113 A/B Trips respective Comp. K-2001 A/B if second
stage discharge pressure is High (20.56 kg/cm2 g)
I-117 A/B Trips the respective Comp. K-2001 A/B if the lube
oil pressure is very low. (0.35 Kg.cm2 g)
Interlock - Ammonia compressor:
35

36. 36