urea brochure 2009
TRANSCRIPT
Transforming the urea processwith continuous innovation
Growth by urea granules
Contact us
For more information on what Stamicarbon can
do for your organization, please contact us at:
Tel.: +31 (0)46 423 7000
Fax: +31 (0)46 423 7001
Email: [email protected]
www.stamicarbon.com
Visiting address
Stamicarbon bv
Mercator 2
6135 KW Sittard
The Netherlands
Mailing address
Stamicarbon bv
PO Box 53
6160 AB Geleen
The Netherlands
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Content
1 About us 4
2 Urea licensing 5
3 A winning product from a winning player 7
4 Innovation 9
5 Safurex® stainless steel: resistant to corrosion 10
6 Stamicarbon’s urea processes 11
6.1 Synthesis 1: Avancore® urea process 14
6.2 Synthesis 2: Urea 2000plus™ Pool Condenser Concept 16
6.3 Synthesis 3: Urea 2000plus™ Pool Reactor Concept 18
6.4 Low-pressure recirculation section 19
6.5 Evaporation section 20
6.6 Waste-water treatment section 21
6.7 Finishing technology 1: Fluid-bed granulation 22
6.8 Finishing technology 2: Prilling 24
6.9 Finishing technology 3: Rotoform urea pastillation 25
7 UAN Process 27
8 Mega Plant Concept 29
9 Full life cycle support 31
9.1 Plant operation 32
9.2 Plant maintenance 32
9.3 Plant improvement and debottlenecking services 33
Supplements
Contact us
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1 About us
Stamicarbon is the global market leader in the development and licensing of urea technology and services. Our solutions are the culmination of generations of high-quality research and in-depth knowledge of our customers’ processes, requirements and operating practices. Around the world, over 230 urea plants have used, or are currently using, our technology. Our innovation is continuous: working in close cooperation with research institutes, suppliers to the urea business, and our licensees, we are constantly developing new technologies and upgrading our existing technologies.
Our expertiseWherever our people are based, they can all draw on Stamicarbon’s more than 60 years of experience in the urea industry. We also work with a number of reputable engineering, procurement
and construction (EPC) contractors and suppliers of specifi c products and critical equipment. Together, this network offers the expertise that enables us to create the best solution for your business.
What we doOur services include:
Licensing and process design Plant improvementPlant commissioning supportEquipment procurement servicesSupply of critical equipmentEngineering services Troubleshooting, both mechanical and operationalEquipment inspectionsTraining
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Our market-leading urea licensing expertise includes the following elements:
Providing technology licenses for new urea plantsTraditionally, many urea plants are built under LSTK (Lump Sum Turn Key) conditions. In these cases, Stamicarbon provides its urea license through one of its licensed contractors, who has been provided with the necessary process license and know-how. All our licensed contractors are carefully selected to ensure they have the capability and experience to implement large-scale ammonia/urea projects. Their names can be found in the supplement at the back of this brochure.
Recently, a number of different contract models have become increasingly important in mitigating project costs and risks. As a result, Stamicarbon has diversifi ed its urea licensing methods so we can tailor our services to the needs of specifi c projects.
Process design package Contractors or customers who obtain a license to conduct the Stamicarbon urea process are supplied with a comprehensive process design package. This generally includes:
Process description Material balance, steam balance and cooling water balance for different operating modes - all with accompanying fl ow sheets
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2 Urea licensing
Piping and instrumentation diagrams (P & ID)Process data sheets for equipment Instrument index, setting list and data sheets Data sheets for safety valves Logic diagrams and functional control diagramsGeneral design and material specifi cations Operating manual
Our comprehensive process design package enables an experienced engineering contractor (who is ultimately appointed by the customer) to:
Carry out the basic & detailed engineering (E)Procure equipment and materials (P)Construct the plant (C)
Thanks to the expertise and capabilities of our licensed contractors, customers’ projects will be executed both professionally and competitively.
Project execution servicesStamicarbon can provide the following services at any point during project implementation - either directly to the customer or indirectly through a contractor:
Contractor guidance and controlAssistance in selection of equipment manu-facturers Procurement and inspection servicesTraining of the customer’s technical staff in plant commissioning and operation, using state-of-the-art plant simulation and other training aids
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to enable urea producers to cope with these changes. Depending on customer requirements, Stamicarbon can develop a tailor-made solution based on proven technology and the best engineering practices. We offer detailed plant-performance studies to our customers to determine revamp needs, plus a variety of revamp technologies and services to ensure that those needs are met. In these sorts of revamp projects, Stamicarbon can license the technology and supply its services and expertise directly to the producer. In turn, the producer can appoint the engineering contractor to perform any required engineering, procurement and construction.
Replacement of high-pressure urea equipmentWhen the high-pressure equipment comes to the end of its life, there is a real opportunity to improve the effi ciency and capacity of a plant. Stamicarbon can provide solutions that not only improve your high-pressure equipment, but also require only minimum changes and minimum downtime in your plant.
Experience us for yourselfStamicarbon is the global market leader in the development and licensing of urea products and technology. We invite potential licensees to visit one of our plants so they can see for themselves how we boost operational fl exibility, reduce maintenance requirements and increase on-stream times. After the visit, we will work closely with you to assess your needs and develop a customized proposal for your urea plant.
Commissioning services, up to and including completion of the performance test runSupply of critical equipmentPlant simulation and optimization
Technology exchange In some cases, customers may require information additional to that supplied in the process design package. To meet this need, we provide customers with any additional information or expertise they require, through training, know-how exchanges and symposia, or other methods agreed with our customers. In cases where our customers need something completely new, we will work jointly with them to develop the required adjustment.
Revamping existing urea plantsIn a dynamic business environment, customers’ needs will shift due to changing market conditions and governmental regulations. Stamicarbon has developed several safe, cost-effective and environmentally friendly revamp schemes
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3 A winning product from a winning player
With a market share of over 50%, Stamicarbon is the world’s leading player in the fi eld of urea licensing. This position is the result of our:
Extensive experienceStamicarbon has over 60 years’ experience in licensing its urea technology. In fact, we have licensed over 230 new urea plants and have completed over 85 revamp projects in Stamicarbon and non-Stamicarbon plants. A complete list of references is available in our Reference List brochure.
Leading innovationsStamicarbon has been at the forefront of urea research and innovation for over half a century.
As a result, we have been able to revolutionize the urea production process several times.
Low costsOur latest urea plants were designed by our task force of experienced engineers, contractors and material and equipment suppliers. In creating a new plant design, the task force used the Urea 2000plus™ technology, Safurex® material, fl uid-bed granulation technology, as well as their extensive experience, gained from completing many successful plant revamps. As a result, plant investment costs were cut by a massive 17% compared to plants using the old CO2 stripping process.
Our competitive advantages include:Low elevationLow investment, operating and maintenance costs, resulting in lower cost price of urea Competitive energy consumption fi gures* Stochiometric raw-material consumption fi gures*Low emissions and effl uents
*The typical consumption fi gures can be found in the supplement at the back of this brochure.
State-of-the-art urea production processesStamicarbon technologies offer customers a variety of benefi ts, including: Excellent performance
Unbeaten synthesis effi ciency with high conversion of ammonia and carbon dioxideLower temperatures and pressures required in the urea production processHigh on-stream times (for both urea melt production and urea granulation)All product quality standards metHigh utilization ratesLong turnaround intervals (3-4 years)Compliant with the most stringent environmental requirements
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Simplicity and reliability Minimum number of high-pressure equipment items and pipingThe only process that requires only one single recirculation stageSuperior corrosion resistance of materials used in plantsStable process and easy to operateUnbeaten lifetime of critical equipmentOption to have an intrinsically safe (zero oxygen) urea process
Flexibility
Single-train capacity allowing for up to 5000 mtpdMultiple synthesis choices: Avancore® or Urea 2000plus™ Pool Process both are available with a pool condenser or a pool reactorMultiple fi nishing choices: Granulation, Prilling and Rotoform pastillation Urea Ammonium Nitrate (UAN) and Ad-Blue/SCR/automotive grade urea solution techno-logies available as an integrated, cost-effi cient design
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Sustainable technologyFor Stamicarbon, sustainability is a precondition of innovation and Safety, Health, and Environment (SHE) awareness is a key condition for sustainable licensing. This focus ensures our technology is effi cient, environmentally friendly, reliable and above all, safe.
CollaborationIn order to create and to improve innovative urea plants, Stamicarbon also collaborates with a number of suppliers of critical equipment to ensure product quality, and we co-develop new technologies with strategic partners. The names of these companies can be found in the supplement at the back of this brochure.
Global reachWith the experience of licensing urea plants in more than 80 countries, we have the tools to meet your requirements - wherever in the world you need us.
At Stamicarbon, we recognize the power of innovation. That’s why the professionals in our Technology Department are always on the look-out for innovative ways to renew, improve and add to the portfolio of products that we offer our customers. Every year, we spend about 6% of our turnover on developing breakthrough innovations.
Working together with R&D groups, universities, customers and suppliers, our Technology Department creates technologies that optimize the urea production process.In the past 60 years, this has resulted in a number of developments that have improved the urea production process.
These include:
Passivation of urea synthesis by airCO2 stripping process25-22-2 materialN/C measurement systemNon-destructive testing techniquesOnline Leak Detection SystemWaste-water treatment sectionUAN ProcessUrea 2000plus™ Pool Condenser ConceptSafurex® stainless-steel material (together with Sandvik)Urea granulation technology (fl uidized bed type)Siphon jet pumpsUrea 2000plus™ Pool Reactor ConceptIntegrally geared CO2 compressorsMega Plant ConceptRotoform pastillation technology (together with Sandvik)Zero-emission technologyRADAR level measurement (together with Vega)Avancore® urea process (introduced in 2008)
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4 Innovation
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5 Safurex® stainless steel: resistant to corrosion
Stamicarbon has a long and distinguished track record in developing superior, cutting-edge urea plant materials.
X2CrNiMoN 25-22-2With the introduction of the high-pressure stripper, a new stainless steel was needed. Together with Sandvik, a Swedish stainless-steel supplier, we developed the X2CrNiMoN 25-22-2 material. This widely used austenitic stainless steel allows higher operating temperatures and is also more resistant to condensation corrosion. However, it remains vulnerable to active corrosion when used in an HP stripper and chloride stress corrosion cracking when used in a high-pressure carbamate condenser.
Safurex®
Despite the success of the 25-22-2 material, Stamicarbon continued the search for ways of developing even better materials. The ultimate breakthrough came in 1996 with the creation of a special duplex steel called Safurex®, also developed together with Sandvik Materials Technology. As this innovative material is highly resistant to corrosion, it does not require the addition of oxygen - enabling an intrinsically safe plant design.
Safurex® offers numerous signifi cant benefi ts, including:
Zero oxygen, making the plant intrinsically safeLower corrosion rates, leading to longer lifetimesNo active corrosionNo stress corrosion crackingNo condensation corrosionNo crevice corrosionBetter mechanical propertiesLower fatigue propertiesImproved weldabilities
What’s more, Safurex® requires a lower investment than traditional materials and offers you a nearly maintenance-free urea plant with a signifi cant longer lifetime than any other commercially available urea process.
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At Stamicarbon, we are committed to the continuous innovation and development of our technologies so we can provide our customers with the best urea production technology available. One acknowledged breakthrough was our Urea 2000plus™ technology - a major improvement on our well-known CO2 stripping process. Urea 2000plus™ is an innovative process that reduces the plant height considerably and simplifi es its overall design, piping and construction. The Urea 2000plus™ synthesis section incorporates either a high-pressure pool reactor, or a high-pressure pool condenser combined with a vertical reactor.
The following chart shows the development of the Stamicarbon urea process over the last decades and the consequences for the plant height.
6 Stamicarbon’s urea processes
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Our latest development is the Avancore® urea process, which further enhances our proven Urea 2000plus™ technology. This process is based on zero oxygen intake and is therefore
intrinsically safe. In the plant height chart the Avancore® technology is shown in a confi guration for large capacities plants with a pool condenser and vertical high-pressure reactor.
The Avancore® urea process
It reduces the required plant height to just 25m. This obviously has brought down investment costs considerably. However the Avancore® process is also available with a pool reactor for urea plants up-to medium capacities.
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Customers can now choose among basic synthesis concepts that use either Avancore® or the Urea 2000plus™ technology.
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6.1 Synthesis 1: Avancore® Urea Process
section, hydrogen or any other combustibles present in the feed to the urea plant no longer pose any risk of explosion. The ammonia emissions will also be kept to an absolute minimum thanks to the absence of passivation air.
RevampsExperiences gained in revamp projects have also led to the incorporation of the following innovations into the Avancore® urea process:
Low elevation lay-out of the synthesis sectionWhile the urea synthesis loop still relies on gravity fl ow, thus offering maximum reliability, the equipment elevation has been reduced, allowing for lower investment.
Reduced-pressure inert washing systemThe vapor leaving the urea synthesis section is treated in a scrubber operating at a reduced pressure. Most of the ammonia and carbon dioxide left after this scrubbing are absorbed in a carbamate solution coming from the downstream low pressure recirculation section. As a result,
The Avancore® urea process is a new urea synthesis concept that incorporates all the benefi ts of Stamicarbon’s earlier proven innovations. The Avancore® urea process combines the advantages of Urea 2000plus™ technology, Safurex® and innovations and experiences gained from revamp projects.
Urea 2000plus™
The Urea 2000plus™ technology already provided the technological advantage of improving heat transfer in the condensing part of the urea synthesis, achieved by the application of pool condensation, and increasing the available temperature difference over the condenser by combining carbamate condensation and urea reaction in one vessel.
Safurex®
The excellent corrosion-resistant properties of the Safurex® material in an oxygen-free carbamate environment, eliminates the need to use the passivation air required in urea processes. Because of the absence of oxygen in the synthesis
Features Avancore®
• No high-pressure scrubber
• Pool condensation
• Synthesis options: pool condenser
or pool reactor
• All gravity fl ow
• Low elevation
• Zero oxygen
• Low maintenance synthesis
• Lower investment
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no additional water needs to be recycled to the synthesis section, meaning that the urea reaction is therefore not affected.
The Avancore® urea process works as follows:
Ammonia and carbon dioxide are introduced to the high-pressure synthesis using a high-pressure ammonia pump and a carbon-dioxide compressor. The ammonia, together with the carbamate solution from the downstream recirculation section, enters the pool condenser.
The major part of the carbon dioxide enters the synthesis through the high-pressure stripper counter-current to the urea/carbamate solution leaving the reactor. On the shell side, the high-pressure stripper is heated with steam. The off-gas of the high-pressure stripper, containing the carbon dioxide, together with the ammonia and carbon dioxide resulting from dissociated carbamate, is fed into the pool condenser.
The minor part of the carbon dioxide entering the synthesis as a feed enters the urea reactor at the bottom in order to produce suffi cient heat for the endothermic urea reaction.
In the pool condenser, ammonia and carbon dioxide are condensed to form carbamate and
a substantial part of the conversion to urea is already established here. The heat released by condensation and subsequent formation of carbamate is used to produce re-usable low-pressure steam.
Downstream from the pool condenser, the urea-carbamate liquid enters the vertical reactor, if required, located at ground level. Here, the fi nal part of the urea conversion takes place. The urea solution then leaves the top of the reactor, all by gravity fl ow (via an overfl ow funnel) before being introduced into the high-pressure stripper. Gases leaving the urea reactor are directed to the pool condenser.
Gases leaving the pool condenser are fed into the scrubber operating at a reduced pressure. Here, the gases are washed with the carbamate solution from the low-pressure recirculation stage. The enriched carbamate solution is then fed into the pool condenser. This enriched carbamate fl ow contains no more water than in earlier generations of Stamicarbon CO2-stripping plants, meaning that the conversions in the synthesis section are as high as ever. Inert gases leaving the scrubber at reduced pressure containing some ammonia and carbon dioxide are then released into the atmosphere after treatment in a 4-bar absorber.
6.2 Synthesis 2: Urea 2000plus™ Pool Condenser Concept
The Urea 2000plus™ Pool Condenser process works as follows:
Ammonia and carbon dioxide are introduced to the high-pressure synthesis using a high-pressure ammonia pump and a carbon dioxide compressor. The ammonia then drives an ejector, which conveys a carbamate solution into the pool condenser. The carbon dioxide feed usually originates from an associated ammonia plant, and therefore always contains hydrogen. This hydrogen is removed by catalytic combustion that uses air. Air also used to be supplied as a passivating agent to minimize corrosion in the synthesis. When using Safurex® material, this is in essence no longer necessary.
In the high-pressure stripper, the carbon dioxide, entering the synthesis as a feed, fl ows counter-current to the urea solution leaving the reactor. On the shell side, the high-pressure stripper is heated with steam. The off-gas of the high-pressure stripper, containing the carbon dioxide, together with the dissociated carbamate, is then fed into the pool condenser.
In the pool condenser, ammonia and carbon dioxide are condensed to form carbamate, and a substantial part of the conversion to urea is already established here. The heat released by condensation and subsequent formation of carbamate is used to produce re-usable low-pressure steam.
6.2 Synthesis 2: Urea 2000plus™ Pool Condenser Concept
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After the pool condenser, the remaining gases and a urea-carbamate liquid enter the vertical reactor. Here, the fi nal part of the urea conversion takes place. The urea solution then leaves the top of the reactor (via an overfl ow funnel) before being introduced into the high-pressure stripper.
Ammonia and carbon dioxide conversions in the synthesis section of a Stamicarbon carbon dioxide stripping plant are high, reducing the need for a medium pressure stage to recycle any unconverted ammonia and carbon dioxide. As a result, the Stamicarbon CO2 stripping process is the only commercial available process that does not require a medium-pressure recirculation stage downstream from the HP stripper.
Gases leaving the reactor are fed into the high-pressure scrubber. Here, the gases are washed with the carbamate solution from the low-pressure recirculation stage. The enriched carbamate solution is then fed into the high-pressure ejector and, subsequently, to the pool condenser. Inert gases and some ammonia and carbon dioxide are then released into the 4-bar absorber.
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6.3 Synthesis 3: Urea 2000plus™ Pool Reactor Concept
The high-pressure scrubbing operation can also be simplifi ed in the Pool Reactor concept by placing the scrubber sphere above the pool reactor and adding the ammonia to the synthesis via this scrubber. This ensures that no separate heat-exchanging section in this scrubbing operation is required.
In the Pool Reactor concept, carbamate from the low-pressure recirculation section fl ows together with the absorbed gases and the ammonia via a sparger into the pool reactor. As the static liquid height ensures gravity fl ow, no high-pressure ejector is needed.
The Urea 2000plus™ Pool Reactor process works as follows:
Unlike the Pool Condenser concept, the Pool Reactor concept combines the condenser and reactor within a single pool reactor. This is achieved by enlarging the horizontal condenser so as to incorporate additional reactor volume. As a result, it becomes possible to achieve suffi ciently high residence times, eliminating the need for a separate vertical reactor, while creating the conditions that will allow the reaction to reach its optimum condition.
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dilute the resultant ammonium carbamate solution can be kept to a minimum, maximizing conversion fi gures for the urea plant. The resultant carbamate solution is fed, via a high-pressure carbamate pump, back to the synthesis as a scrubbing agent in the high-pressure scrubber.
Before entering the urea solution tank, part of the water present in the urea solution is evaporated by further pre-fl ashing. The vent gas from the recirculation stage is practically free from ammonia because it is scrubbed in an atmospheric absorber. The heat required for this section is derived from the condensation of the low-pressure steam produced in the urea synthesis.
This stage recovers the ammonia and carbon dioxide still present in the urea solution coming from the high-pressure stripper. Thanks to the low ammonia and carbon dioxide concentrations in the stripped urea solutions, the Stamicarbon CO2 stripping process is the only process that requires just one single low-pressure recirculation stage.
Coming out of the stripper, the urea solution is fed into the dissociation heater, where most of the ammonia and carbon dioxide are removed. The ammonia and carbon dioxide are then fed into the low-pressure carbamate condenser, where they are condensed. Because the ratio between ammonia and carbon dioxide in the recovered gases is optimal, the quantity of water needed to
6.4 Low-pressure recirculation section
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6.5 Evaporation section
Before the entire urea production process is complete, the urea solution present in the urea solution tank must be concentrated. The urea solution is therefore sent to an evaporation section. The topology of this evaporation section depends on the applied fi nishing section (prilling, granulation or rotoform pastillation). Depending on the requirements of the fi nishing section, the evaporation section may, for example, consist of two consecutive evaporators, where the water in the urea solution is evaporated under vacuum conditions. The remaining urea melt has a urea concentration varying from 96 to 99.7wt%, depending on the requirements of the downstream fi nishing section.
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6.6 Waste-water treatment section
The process condensate coming from the evaporation section, together with other process effl uents such as sealing water from stuffi ng boxes, contains ammonia and urea. All of the process condensate is collected in the ammonia water tank.
From this tank, the water is fed to the fi rst desorber. In the fi rst desorber, the bulk of ammonia and carbon dioxide are stripped off from the water phase by using the off-gas from the second desorber as a stripping agent. The descending effl uent still contains urea and some ammonia. To remove this urea, this effl uent is then fed to the hydrolyzer. The hydrolyzer is a liquid-fi lled column.In the hydrolyzer, the urea, at elevated pressure
and temperature, is dissociated into ammonia and carbon dioxide by the application of heat (steam) and retention time. The process condensate feed is kept in counter-current contact with the steam in order to obtain extremely low urea content in the hydrolyzer effl uent. The remaining ammonia and carbon dioxide in the effl uent of the hydrolyzer are stripped off with steam at a reduced pressure in the second desorber. The off-gases leaving the fi rst desorber are recycled to the synthesis section after being condensed in the refl ux condenser. The purity of the remaining water satisfi es requirements for boiler feed water make-up or cooling water make-up - which means that Stamicarbon urea plants do not produce a waste-water stream.
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granulation technology has been licensed over 10 times for commercial scale plants, including capacities exceeding 3500 mtpd. The plants using this technology are operating at or above their original design capacity, producing superior-quality products that meet all required product quality standards.
Stamicarbon’s fl uid-bed granulation process works as follows:
A urea melt stream with a urea concentration of 98.5wt% is introduced into the fl uid-bed granulator through the injection headers, which are connected to the urea melt line and the secondary air system. Each injection header comprises vertically placed risers fi tted with spray nozzles that spray the urea melt onto the seed particles. The secondary air, required to transport the granules through the urea melt fi lm, is provided by a secondary air blower. Urea formaldehyde is added to the urea melt as a granulation additive and anti-caking agent. This also improves the granule crushing strength.
Film spraying:The design of the melt fi lm sprayers in the granulator
is at the heart of our fl uid-bed granulation technology. These sprayers not only require a minimum amount
of formaldehyde, but they also reduce the amount of dust formed compared to other fl uid-bed granulation
technologies.
6.7 Finishing technology 1: Fluid-bed granulation
Today, the most commonly used fi nishing technology is fl uid-bed granulation, which was commercialized by Stamicarbon in response to changing market needs. Our patented fl uid-bed urea technology is in use in several urea plants.
Stamicarbon’s fl uid-bed granulation technology offers:
Large reductions in formaldehyde content compared to other fl uid-bed granulation technologiesUnprecedented uninterrupted run times, which can exceed 100 days before washing is requiredExcellent product quality (round and uniform, with a smooth surface)More stable operation conditionsLow urea dust formation, resulting in a lower recycle of urea solution to the urea synthesis plant Low opacity at outlet granulation vent stack Substantial savings on operational costs when compared to other fl uid-bed granulation technologies Excellent properties for downstream coating (for specialty fertilizers)
In just fi ve years, Stamicarbon’s fl uid-bed
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to the scrubber as a scrubbing solution. A purge stream is also pumped to the urea-dissolving vessel and recycled to the urea melt plant.
The product from the granulator fl ows through a screen to prevent any lumps from reaching the granulate cooler. The fl uidization/cooling air, which contains some dust, is exhausted from the top of the granulate cooler and is combined with the air from the product cooler and the de-dusting air. This combined stream is cleaned in the cooler scrubber system.
A bucket elevator lifts the cooled urea granules onto screens, where they are sorted according to size. Fine product is recycled to the granulator. Coarse product is crushed to a smaller size and then recycled to the granulator. On-size product is transported to the product cooler, where it is air-cooled in a fl uidized bed cooler or a bulk-fl ow heat exchanger.
The granulator is divided into a granulation section and a cooling/conditioning section. In both sections, fl uidization air is evenly distributed to fl uidize and cool the granules. Seed (recycled) material is introduced into the fi rst chamber of the granulation section. The urea melt is then sprayed onto this seed material. As the granules move through the granulation section, their size is steadily increased by layering until they reach the required granule diameter.
At this point, the product fi nally fl ows out of the granulator. The granules fl ow from the granulation section to the cooling section (without spray nozzles), where they cool down and harden. Fluidization air and secondary air are exhausted from the top of the granulator by means of an off-gas fan in the off-gas line of the granulator scrubbers. In the scrubbers, the air is cleaned using a scrubbing solution, and the cleaned air is exhausted into the atmosphere. The scrubbing solution (a dilute urea solution) is partly recycled
6.8 Finishing technology 2: Prilling
The prilling process works as follows:
The urea solution is concentrated to 99.7% urea in two steps under vacuum. The resultant molten stream is prilled with the aid of a rotating prilling bucket, designed by Stamicarbon. Using an optional technique of seeding when prilling, impact-resistant prills are obtained. These prills are very resistant to degradation during product handling.
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6.9 Finishing technology 3: Rotoform urea pastillation
The Rotoform process offers the following advantages:
Very low dust emissionsSimple solution to realize very low ammonia emissionsVery low power consumption fi gure More uniform productGood crushing strength even without adding formaldehydeFlexible production by switching on/off rotoformer linesLower investment costsPossibility of producing controlled-release urea and mixed fertilizer
The Rotoform-based urea pastillation processMechanically, a single Rotoform unit for urea pastillation consists of a continuously moving steel belt, typically 1.5m wide and 15-20m long (for a 125 ton/day unit), with a drop-former feeding device at one end of the moving belt and a scraper at the discharge end. The feed to the Rotoform is urea melt with a concentration of 99.6wt% and typically branched off from the urea evaporation section downstream from the urea melt pumps.
Urea is introduced under pressure (3 bar) in molten form to the drop former. The Sandvik Rotoform High Speed Drop Former consists of a heated stator and a perforated rotating shell, which turns concentrically around the stator to deposit drops of urea across the full width of the belt. The circumferential speed of the Rotoformer is synchronized with the speed of the steel belt cooler ensuring that the drops are deposited on the belt without deformation and, after solidifi cation, result in regular pastilles with an optimum shape. The rotating shell contains
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Stamicarbon continuously endeavors to improve the urea process and has now introduced the Rotoform process designed by Sandvik Process Systems as a very useful alternative or addition to the traditional fi nishing techniques of prilling and granulation.
The Rotoform process has been successfully employed in the petrochemical, chemical, food and fertilizer industries since the early 1980s and there are currently more than 1400 Rotoform units in operation worldwide.
The Rotoformer principleThe Rotoformer principle brings together the specially designed drop-former with the outstanding features of the Sandvik steel belt cooler. This technology is ideal for removing bottlenecks, for upgrading the prill tower or granulation section, or for the production of specialty urea products (UAS S-urea, micro nutrients). Premium-quality pastilles can be produced at low investment costs, low operating costs and with minimum emissions.
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rows of small holes which are sized to deliver the required product size. The heat released during crystallization and cooling is transferred by the stainless-steel belt to the cooling water. The cooling water is sprayed against the belt underside, absorbs the heat and is collected in pans, cooled in a cooling system (cooling tower) and returned to the Rotoform units. Under no circumstances can the cooling water come into contact with the urea product.
After solidifi cation, the pastilles are smoothly released from the steel belt via an oscillating scraper. The product then falls directly onto a conveyor belt for transfer to storage. The section above the moving steel belt is enclosed with a hood and vented to an existing vent system. There is no visible urea dust emission, only some ammonia vapors which can be easily removed from the very small air fl ow by means of a normal atmospheric absorber. Several Rotoform units can be installed in parallel in order to achieve higher capacities.
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The urea formation is an equilibrium reaction, so the urea solution formed contains unconverted ammonia and carbon dioxide. Stripping with carbon dioxide causes the greater part of these components to evaporate from the solution. Evaporated ammonia and carbon dioxide, together with fresh ammonia and carbon dioxide, are condensed in the pool reactor, the heat from this condensation being used to produce low-pressure steam. The condensed ammonia and carbon dioxide are partly converted into urea and water. In the low-pressure dissociation section, the stripped urea solution is almost entirely freed from ammonia and carbon dioxide. The overhead vapors of the reactor, mixed with off-gases from the dissociation section and the ammonia present in the urea solution from the urea solution tank, are all sent to the neutralization section.
7 UAN Process
The Stamicarbon partial-recycle CO2-stripping process is eminently suitable for the manufacture of Urea Ammonium Nitrate (UAN) solutions. The ratio of unconverted ammonia to urea is such that the required ratio between urea and ammonium nitrate for the production of UAN solutions can be achieved directly. Ammonia still present in the stripped urea solution, together with the ammonia in the reactor’s off-gases, is converted into ammonium nitrate in a neutralization reactor using nitric acid. UAN solution product is obtained by mixing the urea and ammonium nitrate solutions.The Avancore® and Urea 2000plus™ process can both be applied for the Stamicarbon UAN process.
The UAN process works as follows: In the high-pressure synthesis section, carbon dioxide and ammonia are converted into urea in very much the same way as in the previously described processes.
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The neutralization section comprises a neutralizer, an (optional) ammonium nitrate storage tank, a mixing pipe, a UAN storage tank and off-gas purifi cation equipment.
The neutralizer consists of a U-type combination of a circulation tube and a mixing tube with a separator. It operates just above atmospheric pressure. The ammonia-containing gases from the urea plant are fed into the bottom of the mixing tube; the nitric acid is introduced somewhat lower in the circulation tube. Ammonia and nitric acid react exothermically to form ammonium nitrate according to the following reaction equation:
HNO3 + NH3 <-> NH4NO3
Nitric Acid + Ammonia <-> Ammonium Nitrate
The presence of liquid in the circulation tube and of the gas-liquid mixture in the mixing tube causes the fl uid to circulate. The heat from the reaction is used for the evaporation of water and to increase the temperature to about 135°C. The pH of the solution is controlled by the addition of nitric acid. The gas and liquid phases are separated in the separator, the liquid being sent to the (optional) ammonium nitrate storage tank.
In the mixing pipe, the following substances can be mixed:
Urea solution, still containing some ammonia (temperature 110°C) Ammonium nitrate solution, containing some 0.4% HNO3 (temperature 135°C) Ammonia Nitric acidAcidic condensate from off-gas purifi cation
Here again, the heat from the reaction is utilized to increase the temperature and to evaporate water. The ammonium nitrate-to-urea ratio is controlled at about 4:3. The pH is controlled at 5-6pH by means of the nitric acid feed. The resultant UAN solution is either stored or pumped to battery limits.
The off-gases from the neutralizer are treated in the off-gas purifi cation section. Nitric acid is supplied to this section to neutralize any ammonia that is contained in the off-gases from the neutralizers. Part of the liquid effl uent from the purifi er fl ows down to the mixing pipe; the remainder can be sent to battery limits and is generally used in a nearby nitric acid plant.
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8 Mega Plant Concept
Large urea plants require large high-pressure equipment that is diffi cult and costly to manufacture and transport. To reduce urea fabrication costs, Stamicarbon has developed a Mega Plant concept for single-line urea plants that produce capacities of 5000 mtpd. In the Stamicarbon Mega Plant concept, a proportion of the liquid effl uent from the reactor is diverted to a medium-pressure recycling section, thereby reducing the size of the high-pressure vessels needed. In fact, thanks to the Mega Plant concept, the size of the required high-pressure equipment and lines will not exceed the size of equipment needed for a 3250 mtpd pool condenser type CO2-stripping urea plant! A Mega Plant can be built with both the Avancore® or the Urea 2000plus™
technology.
The Mega Plant process works as follows:
About 70% of the urea solution leaving the urea reactor fl ows to the high-pressure CO2 stripper, while the remainder is fed into a medium-pressure recirculation section. This reduced liquid feed to the stripper in turn reduces not only the size of the stripper needed, but also the heat exchange area of the pool condenser. The degree of stripping effi ciency is adjusted to ensure that as much low-pressure steam is produced by the carbamate reaction in the pool condenser as is needed in the downstream sections of the urea plant. About 30% of the urea solution that leaves the reactor is expanded and enters a gas/liquid separator in a recirculation stage operating at a reduced pressure. After expansion, the urea solution is
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heated by medium-pressure steam. By heating the urea solution, the unconverted carbamate is dissociated into ammonia and carbon dioxide.
Our Mega Plant Concept does not need the ammonia recycle section or the ammonia hold-up steps that are commonly seen in competitors total recycle urea plants. This is because the low ammonia-to-carbon dioxide molar ratio in the separated gases allows for easy condensation as carbamate only.
The operating pressure in this medium-pressure recirculation stage is about 20 bars. After the urea solution leaves the medium-pressure dissociation separator, it fl ows into an adiabatic CO2 stripper, which uses carbon dioxide to strip the solution.
As a result of this process, the ammonia-to-carbon dioxide molar ratio in the liquid leaving the medium-pressure recirculation section is reduced, facilitating the condensation of carbamate gases in the next step. The vapors leaving the medium-pressure dissociation separator, together with the gases leaving the adiabatic CO2 stripper, are condensed on the shell side of the evaporator.
The carbamate formed in the low-pressure recirculation stage is also added to the shell side of this evaporator. The heat released by condensation is used to concentrate the urea solution. Further concentration of the urea solution is achieved using low-pressure steam produced in the pool condenser.
The remaining uncondensed ammonia and carbon dioxide leaving the shell side of the evaporator are sent to a medium-pressure carbamate condenser. The heat released by condensation in this condenser is dissipated into a tempered cooling water system. This process forms medium-pressure carbamate that contains only 20-22wt% water. The carbamate is transferred via a high-pressure carbamate pump to the high-pressure scrubber in the urea synthesis section. The urea solution leaving the adiabatic CO2 stripper and the high-pressure stripper are expanded together in the low-pressure recirculation section.
Successful urea plants comply with all applicable rules and regulations and produce products effi ciently and effectively with maximum on-stream times. However, as plants get older, it may become increasingly diffi cult to maintain effi cient production and full compliance. Many urea plants have been designed for a service life not greatly exceeding twenty years. However, such plants can remain competitive due to the depreciated initial capital investment. Well maintained and upgraded with state-of-the-art technology, these plants succeed in producing at competitive cost prices.
To ensure our customers’ urea plants remain competitive, we offer a range of activities and
services covering the complete life cycle of a plant: Plant operationPlant maintenance Plant improvement, including capacity increase
Examples of Stamicarbon’s full life cycle support are:
Corrosion inspection of the critical urea equipmentProcess analyses and plant optimizationDebottlenecking ideas and life studySimplifi cation of the urea process steps for ease of operationSupply of critical equipment itemsSchemes for sustained maximum output
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9 Full life cycle support
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9.1 Plant operation
How do you ensure your urea plant not only operates in a sustainable manner, but also produces its products at maximum capacity and maximum on-stream times? The solution is to optimize equipment and processes. To help customers ensure their urea plant operates with maximum effi ciency, we have developed a range of plant operation services to improve plant performance, production and energy consumption.
These services are usually carried out within the framework of a Plant Performance Assessment. Throughout this assessment, we pay special attention to:
Minimizing ammonia consumptionMinimizing energy consumptionMinimizing effl uentsMaximizing plant on-stream time
9.2 Plant maintenance
Stamicarbon offers a range of services to ensure your urea plant is well maintained. These include:
Corrosion inspectionsWe offer corrosion inspections to assess the general condition of urea plants and to determine the remaining lifetime of tubes, lining and equipment. In addition, recommendations for inspection intervals are provided.
Equipment criticality assessmentIt is vital that producers know the criticality of their equipment (i.e., the probability that it will fail and the probable effects of any such failure). Equipment failure may have not only economic effects, such as costly plant shutdown and repairs, but also serious health, safety and environmental implications.
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Re-lining of high-pressure urea equipmentOver time, the alloy protection lining in high-pressure urea equipment may become so thin that the equipment needs to be replaced. But in fact, replacement is often unnecessary! We are experts in replacing the alloy protection lining in high-pressure urea equipment - extending the lifetime of the equipment by many years. All our re-lining services follow a carefully planned process to ensure minimum down-time and optimum results.
Replacement of high-pressure equipmentChoosing the right replacement for your high-pressure equipment can be diffi cult. That’s why Stamicarbon cooperates with customers to make tailor-made equipment that not only incorporates the most advanced design features, but that is also free of defects and will not cause unnecessary shutdowns.
The Stamicarbon services can include:Tailor-made specifi cation in consultation with the customerPreparation of the Invitation to BidEvaluation (including technical evaluation) of the bids and manufacturer selection together with the customerInspections during fabrication to check compliance in accordance with the Stamicarbon specifi cationsExpediting during fabrication
Stamicarbon can also supply HP equipment and other critical items such as HP piping and its components; RADAR level measurements; an NC meter; and leak detection systems. This will provide you a single point of responsibility for the critical activities of your project and will also reduce the often long delivery times of these items.
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9.3 Plant improvement and debottlenecking services
DebottleneckingOne of the revamp services offered by Stamicarbon is debottlenecking. Debottlenecking will enable your urea plant to:
Take full advantage of the plant’s design marginsBoost urea production with the same number of people and basic infrastructureReduce total fi xed and operating costs, lowering the price of the urea producedImprove the plant’s competitive advantage
Debottlenecking conceptsDebottlenecking your urea plant effectively will depend on the availability of feed, utilities and particular plant limitations. And because the availability of feed stocks and utilities varies from site to site, we have developed several debottlenecking concepts that enable us to meet your exact requirements. Depending on your needs, a combination of debottlenecking concepts can be implemented.
This table details some of the concepts available and the expected capacity increases: Concept type Expected capacity increase %More In, More Out 10 - 25Mega Plant technology 30 - 40Double Stripper 35 - 45Pool condenser/combi-reactor 40 -100
The reference for the given capacity increase is the nameplate capacity. It should be noted that the achievable plant capacity increase depends on the original design margins of the large capital equipment.
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Stamicarbon has carried out more than 85 revamp projects at all kinds of urea plants, including both Stamicarbon and non-Stamicarbon plants. Thanks to a combination of state-of-the-art technologies and expert know-how, our revamp services can dramatically improve plant performance. Our services include:
Increasing plant capacityReducing ammonia consumption and emissionsOptimizing energy consumption Increasing product quality
Rigorous onsite revamp studyAt the start of the process, Stamicarbon performs a rigorous onsite revamp study to determine the present performance of the plant and to design the optimum revamp solution.
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Some examples of debottlenecking projects are:
PIC, Kuwait: Original 550 mtpd total recycle conventional urea plant First debottlenecking to 1065 mtpd with conventional technology Second debottlenecking to 1750 mtpd with pool condenser and CO2
stripping technology
Iffco, Kalol, India: Original 1200 mtpd CO2 stripping plant Debottlenecking to 1650 mtpd with More In More Out technology
Saskferco, Canada: Original 2000 mtpd CO2 stripping plant Debottlenecking to 2850 mtpd with Double Stripper technology
DSM, Netherlands: Original 1100 mtpd Pool reactor CO2 stripping plant Debottlenecking to 1500 mtpd with MEGA technology
Ningxia, China: Original 1740 mtpd NH3 stripping plant Debottlenecking to 2610 mtpd with pool condenser and CO2 stripping technology
Erdos, China: Original two lines of 1000 mtpd TEC TR-C urea plants Debottlenecking to 3520 mtpd with pool condenser and CO2 stripping technology
As these examples show, even plants with relatively small capacities can be debottlenecked. This can cut the cost price of the urea produced.
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Transforming the urea processwith continuous innovation
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Contact us
For more information on what Stamicarbon can
do for your organization, please contact us at:
Tel.: +31 (0)46 423 7000
Fax: +31 (0)46 423 7001
Email: [email protected]
www.stamicarbon.com
Visiting address
Stamicarbon bv
Mercator 2
6135 KW Sittard
The Netherlands
Mailing address
Stamicarbon bv
PO Box 53
6160 AB Geleen
The Netherlands