urea 2000 plus pool condenser and pool reactor

1. Urea 2000plusTM
Pool Condenser
Prem Baboo
National Fertilizers Ltd. India
Introduction
Back in the late sixties, the development of the Stamicarbon CO2 stripping process
revolutionized urea process technology. The introduction of Stamicarbon's Urea
2000plusTM
in 1996, was yet another milestone. By combining equipment, our engineers
have been able to reduce the number of high pressure vessels in the process, thereby also
simplifying the overall design, piping and construction.
The result: a considerable lowering of investments and operating costs.The Pool
Condenser concept was the first step in the development of this technology. A second
step was the introduction of the Urea 2000plus TM
Pool Reactor concept, which has been
built at DSM in Geleen, The Netherlands, with a capacity of 1150 mt/d.
Stamicarbon can offer this process in its pool condenser alternative in single train
capacities up to 3,250 mt/d. This capacity range again signifies an improvement over
today's plants, which have typically been designed for around 2000 mt/d.
The Pool condenser
In the effort to develop the pool condenser, use was made of extensive experience gained
in urea plants of our licensees in which similar condensers are used for different purposes
and from the extensive process database available at Stamicarbon.
Basically, the pool condenser is a horizontal vessel with a submerged U-tube bundle. It is
fabricated from carbon steel with internals and lining in stainless steel.

2. The operating principles are:
 Strip-gases are condensed in a pool of liquid on the shell side, with low
pressure steam being generated on the tube side.
 Adequate residence time allows the reaction of ammonium carbamate to
urea and water to proceed to up to 60 % of equilibrium.
 The condensation temperature on the shell side is high as a result of the
formation of high boiling components (urea and water), resulting in a
higher delta T for the exchanger part. The formation of gas bubbles
ensures a high degree of turbulence and provides a large area for mass
and heat transfer. Both phenomena contribute to a higher heat transfer.

3. The Optimum Reactor Design
The optimum reactor design curve
indicates that as much as 60% of
the fractional approach to
equilibrium (F.A.E.) is reached
already within the pool condenser
whose capacity is only 30 to 40 %
of the required reaction volume. As
a direct consequence, the actual
reactor volume can be considerable
reduced.
The pool condenser design
Process data: Mechanical design data:
 Shell side:
- 140 bar synthesis pressure
- 175 degree C at reactor outlet
 Tube side: 4.5 bar steam/BFW
 Stainless steel vessel
 U-tube bundle
 Internal bore welding

4.  Gas dividing system with flow deflector
plates
 Tube supports
Advantages
The pool condenser configuration offers the following technological
advantages:
 The urea reactor volume is reduced by some 40 %.
 The pool condenser requires some 45 % less heat exchange area.
 The height of the steel structure is reduced by some 10 meter.
 No stress corrosion can take place, because of the absence of crevices
between tube and tube sheet.
 The operational flexibility has improved immensely.
 The start-up of the synthesis section is very easy.
Operational Experience
The pool condenser is used in the urea plant of
Karnaphulli Fertilizers Company in Chittagong,
Bangladesh. The plant has a design capacity of
1725 mtpd and was constructed by Chiyoda of
Japan. It came on stream in December 1994. The
pool condenser concept was selected for this
plant because of its location in the vicinity of
Chittagong Airport. A low skyline of the plant
was a restricting requirement. The pool
condenser allowed the reactor to be made
considerably shorter because the compensating
reactor volume is available in the shell side of the
horizontal carbamate condenser.
In the 4 years of operation this pool condenser
plant is performing on a higher than design load
in a very reliable way.
The 1725 mtpd KAFCO urea
plant with the Pool Condenser,
in operation since December
1994.

5. Technology for the next century
Technology can always be improved. Stamicarbon has again demonstrated that
mature technology can still be innovated. A major development resulting from
the successful performance of the pool condenser in Bangladesh is the
incorporation of all the required retention time for the urea reaction in one and
the same vessel, so creating the new Urea 2000plusTM
Pool Reactor process in
1996. The first Pool Reactor plant with a capacity of 1150 mtpd is in operation
since March 1998 at DSM in Geleen, The Netherlands. The operational
experiences since then are magnificent.
Another large pool condenser is presently under design for the revamp of the
conventional PIC Kuwait plant, tripling the original capacity and at the same
time reducing the steam requirement significantly.
Stamicarbon's objective is to remain the world leader in urea technology. With
our Urea 2000plusTM
technology we can license state-of-the art urea plants with
capacities far above 2000 mtpd for dependable service far beyond the year
2000.
Producers opting for Urea 2000plusTM
technology will be ready for the
challenges of the future.
For further information see:
 CO2 Stripping urea process
 Urea 2000plusTM
Technology
 Urea 2000plusTM
Pool Reactor technology
 References Urea 2000plusTM
 References CO2 Stripping 1990-1999
 Revamping
 Plant Inspection and Equipment Procurement Services

6. Urea 2000plusTM
Pool Reactor
Introduction
Back in the late sixties, the development of the Stamicarbon CO2 stripping
process revolutionized urea process technology. The introduction of
Stamicarbon's Urea 2000plusTM
in 1996, was yet another milestone. By
combining equipment, our engineers have been able to reduce the number of
high pressure vessels in the process, thereby also simplifying the overall
design, piping and construction. The result: a considerable lowering of
investments and operating costs.
Stamicarbon can offer this process in single train capacities up to 3,500 mt/d.
This capacity range again signifies an improvement over today's plants, which
have typically been designed for around 2000 mt/d.
The Pool Condenser concept was the first step in the development of this
technology.The second step was the introduction of the Urea 2000plus TM
Pool
Reactor concept.
The Pool reactor
The introduction of a pool reactor greatly simplified the Urea 2000plusTM
synthesis section. The CO2 stripper was left unchanged to maintain all the
technological advantages of CO2 stripping. However, the stripper off-gases are
now condensed in a submerged condenser forming an intrinsic part of the urea
reactor, which in this combination is now called pool reactor and is installed
horizontally. In this way two complete process steps are combined in one
vessel:
 ammonia and carbon dioxide condensation into carbamate
 dehydration of carbamate into urea

7. The innovative Pool Reactor at the DSM urea plant in The Netherlands
The stripper off-gases, the recycle carbamate solution and the ammonia
feedstock are introduced into the pool reactor. The liquid phase is thoroughly
agitated by the gases from the stripper. The heat of condensation is utilised for
aiding the dehydration reaction and for generating steam in the tube bundle.
The rate of condensation is controlled by the pressure of the generated steam.
The part of the pool reactor that is equipped with the tube bundle is the
condensing part of the reactor while the other section can be called the reaction
part.

8. The Optimum Reactor Design
The optimum reactor
design curve indicates
that as much as 60% of
the fractional approach to
equilibrium (F.A.E.) takes
place in the condensing
part while the remaining
reactor volume provides
the retention time needed
for the urea reaction to
proceed to the selected
F.A.E..
The Cross-Sectional Flow Pattern
The cross-sectional flow
pattern shown here
indicates the flows in a
typical compartment in
the pool reactor. The
pattern confirms the fluid
dynamic calculations and
the location of the gas
sparger, with its two
branches from where
bubbles emerge is clearly
visible. The ascending
flow induces a circulation
pattern from the bottom to
the top and down again
past the deflector plates
flanking the sparger and
the tube bundle.

9. The pool reactor design
Process data: Mechanical design data:
 Shell side:
- 140 bar synthesis pressure
- 185 degree C at reactor outlet
 Tube side: 4.5 bar steam/BFW
 Gas dividing system with flow detector
plates and baffles
 Carbon steel vessel
 Stainless steel internals
and liner/overlay
 U-tube bundle
 Internal bore welding
 Tube support
Advantages
The pool reactor configuration offers the following technological advantages:
 The amount of heat transferred through the condenser bundle in the
reactor is far better than in falling film condensers.
 The baffles in the reactor prevent back-mixing, thus affording the nearest
approach to equilibrium in the urea reaction and, consequently the
highest conversion and most economical downstream equipment sizing.
 The operational flexibility has improved immensely because the inverse
response of the synthesis loop has been eliminated and the synthesis is
far less sensitive to deviations in the N/C ratio.
 The start-up of the synthesis section is very easy and progresses
smoothly.

10. Operational Experience
The first operational experiences with the pool
reactor at DSM have been magnificent. Right
from the initial start-up of the section it became
clear that the fundamental design aspects of the
reactor were correct. The plant produced its first
urea on March 18th, 1998 and apart from a few
teething troubles during the first week and a
leaking flange after two weeks of operation it
has been trouble-free since. After three months
of operation the plant was shut down for an
inspection. This inspection showed a perfect
vessel and no signs of any corrosion were
reported. The new 1150 mt/d DSM urea
plant with the Pool Reactor,
started up in March 1998.
Technology for the next century
Technology can always be improved.Stamicarbon has again demonstrated that
mature technology can still be innovated. The new Urea 2000plusTM
pool
reactor process, while retaining all advantages of the CO2 stripping process, is
considerably simpler, far easier to operate, highly reliable and requires less
capital investment.
Stamicarbon's objective is to remain the world leader in urea technology. With
our Urea 2000plusTM
technology we can license state-of-the art urea plants with
capacities far above 2000 mtpd for dependable service far beyond the year
2000.
Producers opting for Urea 2000plusTM
technology will be ready for the
challenges of the future.
For further information see:
 CO2 Stripping urea process

11.  Urea 2000plusTM
Technology
 Urea 2000plusTM
Pool Condenser technology
 References
Urea 2000plusTM
Technology
CO2 Stripping process
Stamicarbon has once again succeeded in 1996 in greatly improving its CO2
stripping urea process. Having achieved major successes with its original CO2
stripping process Stamicarbon has now significantly reduced the investment
required for a CO2 stripping synthesis section without affecting the investment
for the downstream parts of a urea plant.
Urea 2000plusTM
technology
This investment reduction was achieved in two steps:
The first step was the introduction of the Urea 2000plusTM
Pool Condenser
technology.
A plant based on this technology has been running trouble-free since late 1994
in Bangladesh at a capacity of 1,750 metric tonnes per day.
The second step was the introduction of the Urea 2000plusTM
Pool Reactor
concept.
A 1,150 metric tonnes per day urea plant incorporating a pool reactor was
commissioned at DSM's Geleen site, in the Netherlands, in March 1998.

12. We are proud to have
succeeded in making major
improvements to a
technology which many
considered to be in a mature
stage. This achievement
exemplifies our continuous
commitment to development.
Unique features
The Stamicarbon Urea 2000plusTM
technology
boasts several distinctive features:
 simple and reliable
 fewer high pressure equipment items
 standard rotating equipment
 one single step recirculation stage
 no corrosion
 high on-stream time
 gravity flow
 low cost
 low investment
 low operating and maintenance costs
 lowest raw material consumption
figures
 very competitive energy consumption
figures
 flexible
 single train capacity up to 3,500 mt/d
 both granulation and prilling as
finishing options
 urea ammonium nitrate (UAN) solution
unit may be incorporated
 excellent performance
 safe
 meets the most stringent environmental
Urea Pool Condenser Plant,
Bangladesh
1,725 tonnes per day
in operation since December
1994.
Urea Pool Reactor Plant, The
Netherlands

13. requirements
 meets all quality standards
 proven life times far over 20 years.
1,150 tonnes per day
in operation since March 1998.
No wonder Stamicarbon is the world market leader in urea technology
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