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.

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.

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

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.

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

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

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.

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.

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.

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

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.

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

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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