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Stamicarbon Corrosion in Urea Plants

Registered users
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Explosion risks in urea plants the stamicarbon y2k update

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The combination of growing insight on the one hand, and increasing demands on the other hand, justifies a regular update of safety guidelines and standards. Referring to the present year 2000, we name

d our present update “The Stamicarbon Y2K update on explosion risk in urea plants

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Urea plant Safety - A review

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Process safety of course is a very important topic for all of us. Nowadays we see that worldwide every company working in our industry sets challenging policies and targets to improve on safety perfor

mance. And rightfully; we must see safety as a prime concern in order to protect ourselves and our neighbors from unwanted effects from our activities. Moreover, on the long run production without accidents will be a key factor in order to obtain and maintain acceptance of our activities by the rest of the society. In order to maintain this so called ‘license to operate’ it is of importance that our production processes are safe, but also we should be able to proof that our safety procedures and standards are up to ‘world class’ level. In this respect it is important to recognize that safety standards are continuously evolving. Things that were fully acceptable 100 years ago nowadays are completely unthinkable.

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SAFUREX™ - It was not a dream

Public

This story called: Safurex®, it was not a dream, gives a follow up about the behaviour of Safurex or better, corrosion that not has occurred in Safurex equipment after being exposed to urea over a lon

ger time. We also deal with how both Stamicarbon and Sandvik handle Safurex, how to deal with spare material and even spare equipment.

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A new production route for SAFUREX™ HIP-2

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An all Safurex® urea synthesis loop comprises a number of diverse Safurex® components, which are fabricated by a variety of production methods/routes. These include among others hot extrusion (for HP

piping), cold pilgering (for heat exchanger tubes), hot and cold rolling (for plates) and forging (for bars).During the development of the HIP-ing method for Safurex®, it also became clear that its corrosion resistance was superior to that of non HIP-ed Safurex®. This opens opportunities to use the HIP-ed material in specific applications where higher corrosion resistance is needed. In this paper the development and achievements of this production route are presented as well as the first operational experiences. HIP-ed Safurex® is patented by Sandvik and Stamicarbon.

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Accurate Eddy current wall thickness measurements of SAFUREX™ heat exchanger tubes

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Triggered by the reported higher passive corrosion rate of Safurex® heat exchanger (HEX) tubes compared with BC.05 (X2CrNiMo25-22-2) HEX tubes in HP strippers, an extensive study was undertaken to ana

lyse the accuracy and reliability of the applied inspection method. Together with the introduction of Safurex®, a modified eddy current inspection technology was developed to assess the wall thickness of HP stripper HEX-tubes. After utilizing this inspection technology for a couple a years, the reported higher passive corrosion rates of Safurex® HEX-tubes were doubted, since Safurex® outperforms BC.05 material in all laboratory corrosion tests. Proper understanding of the modified eddy current inspection technology resulted in a more reliable and accurate inspection technique. By using this optimized procedure, the corrosion rate of Safurex® HEX-tubes is currently reported in the same order of magnitude as the BC.05 ones. Still a distinct advantage of Safurex® over BC.05 HEX tubes in HP strippers is the absence of active corrosion, which makes the use of the former far more favorable .

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EXPERIENCES AND NEW DEVELOPMENTS IN SAFUREX™ STEEL

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Forms of corrosion in Urea Syntheses in fully austenitic stainless steels: 1) Overall attack (passive or active) All vessels 2) Crevice corrosion All vessels 3) Condensation corrosion All vessels

4) Stress corrosion cracking Typically vertical HPCC 5) Strain induced intergranular cracking Typically Urea Reactor 6) Stern face attack Typically HPCC & Scrubber 7) Under deposit corrosion Typically HP Stripper

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GMA welding process for SAFUREX™ liners

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Based on the results of the program, Stamicarbon considers the special semi-automatic GMA welding process validated and has approved it as an alternative welding process for liner welding. It will be

included in the Stamicarbon Specification A4-71111 for welding of Safurex® liners. 

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SAFUREX™ experiences and developments

Registered users

1. More flexibility in plant operations • Oxygen passivation not needed • Turndown ratio not critical • Blocking in time not critical 2. Less inspections, longer inspection intervals (6 years) 3. Less

maintenance and repairs; lower OPEX costs 4. Lower APEX

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Re-linen of Urea Reactors in-Situ

Restricted

Operating an urea equipment over many years will lead to thinning of the alloy protection. This thinning takes place gradually and is not for all equipment identical. Even a difference of corrosion is

taking place within a single piece of equipment. In a Urea reactor for instance the corrosion in the top is more than in the bottom part. This reduction in liner wall thickness should not mean automatically the end of the lifetime of a reactor. An in situ relining may extend the lifetime of the reactor again for many years. To allow an optimum repair with respect to quality, timing and down time of the Urea reactor it is important to make a good game plan and preparations should already be done prior to the turn around. In the HP Heat Exchangers the liner is not the critical factor. The heat exchanger tubes are the limiting factor with respect to the lifetime of the equipment and a replacement appears to be the most economical solution.

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Advance insight digital solutions to optimize your plant peformance

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Advance Equipment Inspections

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• Introduction Advance Services • Inspections • Repairs • Supply of Equipment • Summary

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Agrium CNO HP stripper History and Key learning's

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A High Pressure Stripper operated for 20 years in the Agrium Carseland Nitrogen Plant sustained an unusually high number of tube ruptures. The history and analysis of each tube failure is reviewed in

the report. Conclusions and recommendations based on key learning’s are given.

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Biuret is back on the agenda after 40 years

Registered users

Due to the fast increasing market of Diesel Exhaust Fuel (DEF, AdBlue®, ARLA 32), biuret is becoming a hot topic again.  DEF is a 32.5 wt% aqueous urea solution used as de-NOx agent to remove NOx

out of the exhaust of diesel cars. Diesel trucks but also already private cars are obliged to use DEF in Europe and the US, more continents will follow. The price of DEF at the moment almost doubles the price of urea fertilizer. All urea producers are looking for opportunities to become part of the DEF family. The DEF specification is described by ISO 22241 and DIN V70070 and limits amongst others the amounts of Biuret (< 0.3 wt%), NH3 (< 0.2 wt%) and Formaldehyde (< 5 ppm). DEF is produced by urea producers as a 32.5 wt% - or a 50 wt% aqueous urea solution or as solid product depending on the distance between the producers and the consumers. Urea granules are abandoned as DEF due to its formaldehyde content. Urea prills are sold in China as premium if the biuret content is maintained lower than 0.9 wt% because in that case they can be used for DEF.  Plants with a granulation finishing section which produce DEF from urea solution have difficulties to keep the biuret concentration low enough in their granules due to the increased residence time in the evaporation stage. These challenges are leading to the increased worldwide interest in biuret.

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Fifteen years SAFUREX™ in Stamicarbon Urea Plants

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Since 1998 Safurex® equipment are in operation and Stamicarbon has gained extensive in-service experiences with the corrosion behavior of Safurex®. In this paper the behavior of Safurex® will be compa

red with the corrosion behavior of the traditionally used fully austenitic stainless steels (316L UG [BC.01] and X2CrNiMoN 25-22-2 [BC.05]). 

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From urea to Uas to Multiproduct Granulation

Registered users

Because of increasing demand for granulated urea containing macro- and micro-nutrients, Stamicarbon  has developed a unique and flexible process for the production of granulated urea containing &

nbsp;ammonium sulfate. Given the flexibility of this process, it can well be used to also produce  granulated Urea containing other nutrients. This paper gives the background and highlights the  technology, the design and the current status of the process.

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HP reactor vessel wall breech due to loss of passivation at medicine hat

Registered users

The loss of the passivation layer on the liner led to the corrosion.  The loss of passivation occurred during the 22 hour period between the 2nd and 3rd startups, when the dissolved oxygen in the

stagnant process liquid was driven off by generation of heat in the R-101.  The heat was generated when CO2 leaked into the synthesis loop through a passing isolation valve, and the CO2 reacted to form carbamate.  The carbamate reaction generated the heat.  The de-oxygenated process liquid then destabilized the passivation layer and stripped it away, leaving the unprotected stainless steel liner exposed to the highly corrosive carbamate following the 3rd startup. The pinhole and pits were repaired, and the Plant resumed production on July 28th.

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Hydraulics improvement of synthesis loop for sustainable Urea production at high load

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Karnaphuli Fertilizer Company Limited (KAFCO) operates a 1500 mtpd ammonia plant (Haldor Topsoe design) and a 1725 mtpd urea plant (Stamicarbon design) on the bank of the river Karnaphuli in Chittagon

g Bangladesh. It is the first Stamicarbon urea CO2 stripping plant featuring the pool condenser technology, see [1]. In the Kafco-Bangladesh plant, the interconnection between the pool condenser and the reactor is provided by two high pressure (HP) pipelines, a 10” inch liquid and a 10” inch gas line. The plant is commissioned in 1994. After commissioning, operating experience learned that the gas line from the pool condenser to the reactor was sometimes filled with a stagnant liquid level; especially in case of a start-up from a “blocked-in condition“. This resulted in problems with the synthesis hydraulics and limited the maximum plant load to 115%. This problem was mostly overcome after draining of the synthesis loop but causing some environmental problems as well. For a permanent solution to this problem a modification of the HP gas line was implemented during the planned turnaround in 2010.The modification improved the hydraulics of the urea synthesis loop; eliminated gas flow restriction after a “block-in situation” and resulted in an increase of production up to 121% of the design capacity. The 1725 MTPD plant is now able to produce 2100 MTPD.

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New Overpressure Protection System for the Urea Synthesis.

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The motivation for the development of the New Overpressure Protection System for the Urea Synthesis results from the following safety-related and process-related facts: Urea plants in Germany be

long to the so-called accident plants. For these plants it is required that the security is improved constantly. The management wants to constantly improve the environmental-protection andupgrading the technological conditions to increase the production and to save energy.

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Online operational services risks and rewards

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In this presentation Stamicarbon’s vision on providing future value-adding operational services to urea plant owners and operators is presented. Networked computers are envisioned to play an essential

role in realizing this vision. Stamicarbon fully …

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Panel discussion maintenance & corrosion

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Report of the steps description

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Safety and Product Stewardship in the Fertilizer Industry

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I believe the fertilizer industry has a prosperous future. By 2050 it is estimated that 70% more food will have to be produced compared to today. This will demand a continuous growth in fertilizer pro

duction. At the same time, we must expect that society will focus even more on safety and environmental issues associated with fertilizers, such as Health and safety risks from working in fertilizer plants Major accident risks, to avoid disasters like the explosion in Toulouse Terrorist acts, using fertilizers for bomb-making Pollution risks from the manufacturing processes and from the use of fertilizers Climate change and the role of fertilizers and agriculture Use of limited energy and mineral resources, such as phosphates The public perception of Good Citizenship has changed over the years. Today, many people look upon the chemical industry as a burden to future sustainability. This perception will deepen if the industry has a poor safety and environmental performance. It is vital to perform well and to eliminate bad practices. Otherwise we must expect that much stricter regulations will be enforced upon the industry. In this paper I will focus on the 3 first bullet points above, those that are related to safety and product stewardship, with some practical advice on actions the industry should take in order to be in command and avoiding over-regulation. 

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Short delivery to replace an unreliable HP Scrubber

Registered users

In a Stamicarbon 1800 mtpd Urea CO2 stripping plant, commissioned in 1993 a leak was observed in the HP Scrubber 2-E203 by means of a small increase of the conductivity in the closed cooling water sys

tem (CCW). The HP Scrubber is equipped with 316 L UG heat exchanger tubes (BC.01 according Stamicarbon Specification A4- 18005). The presence of ammonia in the CCW indicated a leak from tube side (process side) to the shell side (cooling water side). In contrary to the frequent cases of chloride stress corrosion cracks (Cl- SCC) observed in HP Carbamate Condensers, Cl- SCC cracks are seldom observed in HP Scrubbers. The integrity of the said HP Scrubber was compromised, since it was not possible to pinpoint and repair the leak. It was decided by plant management to replace the HP Scrubber as soon as possible. Schoeller Bleckmann Nitec (SBN) in Austria was awarded the contract to supply a new HP Scrubber with a delivery time of only 8 months. Normally a delivery time of 10 to 12 months is anticipated. In order to meet this very short delivery time, SBN and Stamicarbon teamed-up to speed up the engineering and fabrication work. HP Scrubber was transported from Austria to the Middle East by airfreight. In this contribution the difficulty to locate a small leak is described as well as the key issues to manufacture the new HP Scrubber within such short delivery time. 

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