Friday 13 April 2012

2011 AIChE Ammonia Safety Symposium Questions & Answers -PART 1





Paper 1a:   Major Ammonia Leak Incident in Urea Plant.

 

Presenter:  S. G. Gedigeri and K. M. Babu - OMIFCO, Oman


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By :    Muhammad Afzaal - Fauji Fertiliser Company Limited, Pakistan
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Q 1a.1 :          Did you have any Preventive Maintenance / Inspection plan before hand? I think the weld joint’s health should have already been identified before failure.
A 1a.1 :          OMIFCO plants are relatively new and are in commercial operation since last six years only. OMIFCO is carrying out risk based inspection for static vessels and rotary equipment in major shutdowns. For high pressure piping handling toxic or flammable fluids only random inspection is done based on industry experience. Before the incident we have not checked this particular weld joint. It is not an industry practice and is impossible to inspect all the welds in a mega complex like OMIFCO.

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By :    David Firth – Quest Integrity NZL Limited, New Zealand
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Q 1a.2 :          Comments made were that the fatigue performance was probably reduced as a result of incorrect PWHT (as the hardness was excessive), the original installation (as there was a significant offset after the failure), thermal expansion and vibration. What extent of vibration monitoring & vibration modeling was carried out?
A 1a.2 :          In our regular vibration monitoring program only rotating equipment have been covered so far. If any rotating equipment is found with very high vibrations or the associated suction/discharge piping are  visually found to vibrate, then along with the equipment its associated piping are also analyzed for vibrations.

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By :    G. K. Gautam – IFFCO - Aonla Unit, India
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Q 1a.3 :          Has the welding record been checked for subject weld whether proper PWHT has been carried out properly & welding consumables of right quality have been used.  What is the impact of clamp on stress on pipe weld.
A 1a.3 :          OMIFCO plants were set up under the EPCC contract awarded on international competitive bidding procedure. OMIFCO’S takeover of the plants took place after the completion of the initial warranty period. The welding records could not be traced as the contractor gave some jobs on sub contracts also. But OMIFCO believes that the contractor has adhered to the approved WPS as prescribed by the process licensor.

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By :    Carl Jaske – Det Norske Veritas, USA
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Q 1a.4 :          When the initial leak was found and clamped, did you perform an engineering  assessment of fitness for service and remaining life. It seems that this would have found the problem before the break occurred?
A 1a.4 :          The pipe thickness nearer to the leaky joint was checked and found to be as per the specification. The weld joint could not be inspected due to the persisting Ammonia leak and the urgency of arresting the leakage to control the environment contamination.

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By :    Danny Franceus – Yara, Belgium
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Q 1a.5 :          What are your recommendations for Adaptation of Inspection Program towards other plants?
A 1a.5 :          Good healthy condition of the paint or insulation of the piping should be ensured by regular monitoring. If any damage of the Insulation or paint condition noticed it should be attended immediately after inspecting/assessing the condition of the exposed pipes. To take care of damage occurring from inside of the pipe the thickness of all critical piping should be examined by pre-decided schedule and planning at strategic locations by providing corrosion monitoring windows/coupons.

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By :    Saleh Said Al Habsi – OMIFCO, Oman
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Q 1a.6 :          What is the best method to attend Ammonia Leak from Ammonia Pipeline?
A 1a.6 :          We understand this depends on the specific situation depending on the quantum of leakage, operated pressure of the failed leaky portion and the contained quantity of Ammonia handled by that piece of equipment. Where ever high pressures and higher volumes are involved it might be prudent to isolate or stop the facility and repair it.

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Paper 1b:   Major An Alternative Approach for Leak Before Break Assessment to Postpone the First Internal Inspection of a Refrigerated Ammonia Storage Tank.

 

Presenter:  Alex Scheerder - Stamicarbon bv, The Nethrlands

Pascal Schreurs – Sintra Engineers bv, The Netherlands


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By :    Mike Antony – ProPlant Inc., USA
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Q 1b.1 :          The approach does not include bottom plate circumferential weld with floor plate.  Recent inspection of a 10,000 MT tank had failures all around (360 Deg) this weld. Number of other inspections has revealed the same.
A 1b.1 :          This is correct; in the present EFMA guideline the bottom circumferential weld with floor plate is not included. We question this approach and we propose the EFMA to include the critical weld in the guideline.  We already did some fracture mechanical analysis in a similar ammonia tank and concluded that indeed this weld is critical.

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By :    Muhammad Abdullah – Fauji Fertilizer Company Limited, Pakistan
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Q 1b.2 :          What kinds of NDTs are employed for checking the health of the Ammonia Tank at your plant.
A 1b.2 :          In the tank under investigation following NDE has been performed:
                        Visual inspection of the outer tank wall; check for failures in painting system
                        UT examination of outer tank wall, at random
Visual inspection of tank foundation, settlement measurements
Infrared thermography of tank wall for leakages


 

Paper 1d:   Operator Training Simulator in Ammonia Plants:

Increase safety, Decrease Cost, and Strengthen Competitiveness

 

Authors :    Klaus Schübel - SKW Stickstoffwerke Piesteritz GmbH, Germany

Norbert Ringer, Kisnaduth Kesore - Süd-Chemie AG, Germany

Marco Lanteri, Massimiliano Morniroli - APC Tech, Italy

Gregor Fernholz - Invensys Operations Management, Germany

 

Presenter:  Klaus Schübel - SKW Stickstoffwerke Piesteritz GmbH, Germany Norbert Ringer, Kisnaduth Kesore - Süd-Chemie AG, Germany

Gerry Mak - Invensys Operations Management, U.K.

 

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By :    Shafi Ahmed – Karnaphuli Fertilizer Company Limited (KAFCO), Bangladesh
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Q 1d.1  :         1.  Time period for OTS implementation, 2.  Cost of OTS implementation, 3. Manpower from owner side.
A 1d.1 :          The time and cost for OTS implementation is highly dependent on the scope of the project. Invensys would be happy to discuss your individual requirements.
The SKW project started in March 2008 and the acceptance test was finished in July 2010. During the entire period an average three SKW specialists were involved (project manager, chemical engineers, experienced plant operator).
In the first year of operation you will need 2-3 employees to operate the OTS (trainer, hardware maintenance, chemical engineer)

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By :    Dorothy Shafer – Baker Risk
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Q 1d.2 :          Since the objective of the simulator was to improve operator response during trips and emergency conditions, did you include alarm management reviews as part of the project to reduce distraction from unnecessary or unimportant alarms?
A 1d.2 :          We know very well, that a successful alarm management is very import for safe and economic operation of an ammonia plant. The OTS was part of a project, which included a copy of the actual version of Foxboro I/A system for both ammonia plants, and we are going through the first steps of improving the alarm management.

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By :    Malika Nait Oukhedou – Protomation, bv
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Q 1d.3 :          a) How much money have you (SKW) saved since the usage of the OTS upto now?
b) How and where are the Trainees results being saved
c) How is the communication done between Sud-Chemie’s Reaction Kinetics & Thermodynamics and the dynamic model?
d) The one million USD that was mentioned, does that include DCS hardware & software in case the concept is a direct – connect solution?

A 1d.3 :          a) It is difficult to answer this question. The economic effect goes in different directions: To avoid critical situations, to operate critical situations better, to operate the plants closer to the optimum, to reduce the time for education of new operators. It is impossible to decide accurate how much of the success of the production is caused by the use of an OTS.
b) The Trainees results are documented in separate files, which contain all necessary information.
c) The OTS replicates the equations from Sud-Chemie directly in the simulation; there is no requirement for communications with an external Kinetic/Thermodynamic model. A lot of cases were run and regression equations were created.  Sud-Chemie has validated the performance of the representation implemented.
d) The price for an OTS depends as remarked earlier, on a lot of things. In our case it included not only the software and hardware, but also costs for buildings and maintenance support and software upgrading costs for the next years.

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By :    Dr. Hans H. Wagner – Ineos Enterprises, Germany
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Q 1d.4:           How many OTS are in operation in the world?  Will this be becoming an industry standard?
A 1d.4:           Invensys has delivered hundreds of operator training simulators around the world, in many different process areas including refineries, petrochemical, oil and gas, pharmaceutical, chemical and power generation. It is rapidly becoming an industry standard, especially in the case of new plants and control system updates. In Europe there are three OTS for ammonia plants in use, as far as we know.

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Paper S2:   ID fan Low Flow problem and Repeated shaft failures of Semi-Lean Pump

 

Authors :    Iftikhar Hussain Turi and Tamvada Srinivas - Qatar Fertiliser Co

 

Presenter:  Iftikhar Hussain Turi and Tamvada Srinivas - Qatar Fertiliser Co

 

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By :    Muhammad Abdullah – Fauji Fertilizer Company, Bangladesh
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Q S2.1 :         When low flow problem was being observed ? Did you check the vibration level at fan casing.
A S2.1 :          There  was  slight  increase in overall  vibration  during low flow . But with vibration analysis the problem with cone setting cannot be pin pointed. Flow related vibration can be due to many reasons.
The method we used measured the actual flow accurately & we could see the difference with Ammonia 2 fan clearly.
To  stop the  plant for 5  days  to correct the cone  settings  required  a  method  to be 100 % accurate as  justification.

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By :    Harrie Duisters – OCI Nitrogen
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Q S2.2 :         Can you better explain, how the extra vent works ?   
A S2.2 :          It is only for priming the pump at start up to vent the air trapped below  suction valve.

Q S2.3 :         Is it only for start-up?  No valves in vent line (see figure  2 ) ??

A S2.3:              The vent is only for initial priming, at start up . It has a valve at the platform level for the suction valve. It can be seen in photo 7 in the paper.

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Paper 2c:     Rupture of the primary reformer-mixed feed coil header at Tringen1

 

Authors :     Stenn Mowassie and Laurent Ruhlmann -YaraTrinidad

Michael Schlaug - Yara International SA, Norway

 

Presenter:     Stenn Mowassie -YaraTrinidad

 

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By :    Dorothy F. Maxwell Shaffer – Baker Risk
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Q 2c.1 :          Was the reforming catalyst unaffected?
A 2c.1 :          Yes, the reforming catalyst was essentially unaffected. Post outage performance assessments on the reforming catalyst did not show any evidence of reduction in activity or increase in pressure drop.  


Q 2c.2 :          Did you have a previous history of PSV failures on pre pop testing – and is there a policy to investigate those?
A 2c.2 :          No we have not had specific historical problems of PSV failures on pre-pop testing. Our policy now includes a shop test and re-certification of all relief valves known to have lifted in service. This applies even if the relief valve in question appears to have reseated.


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By :    Abdul Rahman Al Hats – OCI Nitrogen
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Q2c.3 :           Did the modification of the MOV inlet of HTS communicated and agreed by the Licensor of the Plant ?   

A2c.3 :           The modification of the inlet MOV to the HTS followed the internal Management of Change process  and did not directly involve the Licensor (Fluor) of the plant.

Q2c.4 :           What will be the modification to prevent the repetition of the same problem?

A2c.4 :           The main modifications to prevent repetition are as follows:
1)   Since the HTS inlet MOV can act as a sectioning valve for the plant, it is proposed to have pressure controlling vent valves installed between all main process sectioning valves. Therefore the installation of a pressure control vent valve from upstream of the HTS inlet MOV to the vent header will be implemented.
2)   Reinstallation of position alarms on HTS inlet MOV and verification of the  functionality of all other major process MOV’s position alarms.
3)   Upgrade the pressure relief valve sizing on the HTS inlet. Each valve will be sized for 100% relief capacity therefore resulting in a 2 x 100% relief arrangement.
4)   Change in policy – Relief valves are to be shop tested once the valve has lifted to verify that the valve integrity and functionality has not been compromised


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By :    John Mason – Agrium Inc., Canada
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Q2c.5 :           In addition to reviewing need for additional redundancy in the pressure relief valves, are you reviewing or considering any changes to the relief valves (metallurgy, style) ?   

A2c.5 :           Yes. This will be taken into account as part of the Management of Change process. The intention is to solve the root cause for both the sizing issue as well as the mechanism  causing damage on lifting.

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By :    Harrie Duisters – OCI Nitrogen
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Q 2c.6 :          Can we get a copy of the power point presentation for operator training?   

A 2c.6 :          Please contact treveno.mowassie@yara.com to discuss the specifics of any requests.





Paper 2e:     Failures of Pigtails: Why They Happen and How to Avoid Them

 

Authors :     C. W. Thomas and M. J. Smillie - Quest Integrity Group

 

Presenter:     M. J. Smillie - Quest Integrity Group

 

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By :    Reinaldo Caldera V. – Petroquimica de Venezuela (Pequiven), Venezuela
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Q 2e.1:           Did you replace the Pigtails?
A 2e.1:           The plants whose pigtails were removed for destructive sectioning did replace those pigtails.  Pigtails in general are often removed (and replaced) on criteria based on condition or inspection metrics e.g. measured expansion of the tubes and on history. Numerous failures at the pigtail terminal welds for example may lead to a decision to replace all pigtails


Q 2e.2:           What material for pigtail are you going to use for the next purchase order?
A 2e.2 :             Our clients have not gone away from Alloy 800H/HT (or equivalent alloys).  Careful specification of the alloy composition, grain size and pigtail manufacturing processes allows greater confidence of the performance in service.             

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By :    Kang Xu – Praxair
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Q 2e.3:           Recommendation on the optimal grain size range for 800 HT?
A 2e.3:           The actual grain size specification will depend on design (e.g. number of bends), temperature in service, inspection requirements and expected performance.  Certainly, to avoid low ductility cracking, grain sizes no coarser than ASTM Number 1 or 2 may be desirable.  The optimal range is as little variation in grain size as possible given the limitations of manufacturing (e.g. grain size control during bending and annealing operations).  That will vary from vendor to vendor.


Q 2e.4:           Comment on API 530 LMP which treats 800, 800 H, and 800 HT the same?
A 2e.4 :             I think that API will distinguish between the base Alloy 800 and the 800H and 800HT variants. Data for Alloy 800 is not included in API 530 or API 579 and Alloy 800 would normally be considered a low temperature alloy for corrosion resistance. I understand API considered Alloy 800H and HT to have the same material performance under the design criteria of API 530, as a way to accommodate the apparent variability of the creep performance of Alloy 800HT under certain operating conditions.  The API 530 Material Data Book does provide separate LMP curves for Alloy 800H and Alloy 800HT.

 

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Paper 3a:     Successful Operating Experience of CFCL Ammonia Plant Revamped with KBR KRESTM Technology

 

Authors :     Upendra Singh - Chambal Fertilizers and Chemicals Ltd, India

Shashi Singh and Avinash Malhotra - KBR, USA

 

Presenter:     Upendra Singh - Chambal Fertilizers and Chemicals Ltd, India

Shashi Singh - KBR, USA

 

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By :    C. M. T. Britto – Rashtriya Chemicals and Fertilizers Ltd., India
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Q 3a.1:           During the presentation you said that there was a hot spot in KRES which was fixed. Can you please elaborate on this problem and how it was fixed?
A 3a.1:           The hot spot at the top was caused due to an internal dent on a metal part happened during equipment’s road transportation. This was leading to higher than usual metal temperature. Unit was kept operational without any impact on ammonia production rate, external steam sparger was used. This problem was completely solved by repairing the affected part in the annual shutdown of April 2010


Q 3a.2:           What are the major equipment changes that will be incorporated while revamping from GV to aMDEA system during 2nd stage revamp? Does it involve significant Capital investment?
A 3a.2 :          This requires new absorber, LP Flash vessel and some semilean pumps. Capital cost as well as execution during shutdown is significant. We knew these aspects from the conceptualization stage, but significant benefits of the 2stage MDEA process had convinced us to follow this feature. Also we know other ammonia plants have implemented such a revamp and have benefitted in long run.

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By :    K. M. Babu – Oman India Fertilizer Company, Oman
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Q 3a.3:           What is the pressure drop profile between Primary Reformer inlet and RG Boiler inlet before and after KRES installation?
A 3a.3:           Pressure drop values between these two points at base case and post revamp are 3.5 and 2.0 kg/cm2 respectively. Plant load post revamp is 1781 (vs. base 1608) MTPD as described in the paper. Pressure drop does not increase with production throughput since the reforming exchanger is added in parallel.


Q 3a.4:           What is the temperature profile of Secondary Reformer before and after KRES installation?
A 3a.4 :          Temperature of the gases at the very top during and after combustion is slightly higher as flow rate of process air relative to the reformed gas is relatively increased. Final outlet temperature is slightly more or similar to before per overall operations. The new conditions are easily handled in the secondary reformer as is proven over two years of operation in CFCL and off-course earlier in the previous two KRES units that followed the scheme without primary reformer as explained in the paper.
           

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By :    Venkat Pattabathula – Incitec Pivot Ltd., Australia
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Q 3a.5:           How was the dP across KRES – SOR and current?
A 3a.5:           The dP across KRES was about 1.0 kg/cm2 at SOR and about 2.0 kg/cm2 currently. Since reforming exchanger works in parallel to primary and secondary reformers, pressure drop is not an issue. The reforming exchanger is able to operate with dP of up to 4 kg/cm2.


Q 3a.6:           What about Nox levels in Reformer stack?  Have they come down?
A 3a.6:           Total Nox level inside the ammonia plant is related to fuel firing in the furnace, hence it comes down in line with the reduced firing in primary reformer. Overall whole complex Nox is expected to be less with overall energy savings.

Q 3a.7:           Add on converter design.  Hot wall  or Quench Gas Cooling of shell?
A 3a.7:           It is a Hot wall design, i.e. converter pressure vessel has same temperature as the feed gas has.

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Paper 3b:   Woodward, Oklahoma Ammonia Converter Revamp:

More Efficiency and Reliability through Innovation

 

Authors :    Debra Lawrence - CF Industries

Jamie Ballard - Süd-Chemie, Inc.

Francesco Baratto - Ammonia Casale S.A.

 

Presenter:  Debra Lawrence - CF Industries

 

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By :    John Mason – Agrium
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Q 3b.1:           Have you quantified the benefit of the converter internal replacement vs. replacing the catalyst?  In other words, what percentage of benefit is from the new internals and what percentage can be attributed to new catalyst?
A 3b.1:           It is difficult to separate and quantify the improvements based on the new internals vs. the new catalyst. Another aspect is the fact that we had bypassing occurring in the packing gland at the outlet as well as some bypassing in the internal heat exchanger prior to changing out the internals.  We believe the bypassing in the packing gland at the cold-shot and outlet was occurring when the S-200 basket was initially installed. We found that a “retaining ring” was missing when we removed the old internals. So we cannot really fairly compare Start-of-run conditions from the new catalyst and old catalyst.  Another aspect of comparing the Start-of-run conditions of the previous catalyst and the new catalyst is we were not making methanol at the start-run with the previous catalyst and we were making methanol at the start-of-run with the new catalyst and that has an effect on the production rates.  When we are making methanol our inlet inerts to the converter is about 5% higher than when we are not making methanol and of course that will have an effect on the converter performance.

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By :    Harrie Duisters – OCI Nitrogen
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Q 3b.2:           What is the performance of the Amomax-10 catalyst after 2 years of operation?
A 3b.2:           At this time the performance is very satisfactory.  We believe we may even had a CO/CO2 poisoning event (from the methanator) that may have affected the performance, but it appears that the catalyst recovered from the poisoning. Even now after 2.5 years on-stream, the catalyst activity is basically at the expected level for this time onstream, and also above the expected magnetite performance for this time onstream.

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By :    Upendra Singh – Chambal Fertilisers and Chemicals Limited, India
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Q 3b.3:           What is the volume of catalyst in new converter?
A 3b.3:           1362 ft3

Q 3b.4:           What was the final reason for the decision of choosing Amomax-10 catalyst?
Did you look for commercial references of the catalyst in any plant?
How long are these references?
A 3b.4:           One of the reasons was that the Amomax-10 has less water make during the reduction at initial startup. Another reason, costs was a factor but not a major factor. Yes, we did talk to another Amomax-10 customer.  Of course the time in service was not very old since Amomax-10 hasn’t been in use but just a few years. But in talking to the reference we found that time in the startup heater after shutdowns was greatly reduced as well.  At the time, there were references that were almost 5 years old, which was long enough to be deemed commercially successful.

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By :    Glenn A. Combs – Chem-Engineering Services, USA
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Q 3b.5:           Could you please explain why the post retrofit single pass conversion was only about 12.8%? Many plants with inter-cooling have 14-16% single pass conversion?
A 3b.5:           The Flour design plant uses an aqua ammonia refrigeration system. Normally, a refrigeration compressor with a closed loop refrigeration system is employed, therefore a refrigeration compressor is not used, and instead has an aqua/ammonia refrigeration unit.
The main advantage is a cheaper ammonia product, since there is a big cost saving in not having to generate the large quantities of steam that would be necessary to drive a refrigeration compressor.  But as a result of the unconventional aqua/ammonia refrigeration unit, the syngas entering the ammonia converter contains about 4.0 mol% ammonia.
Moreover, the inert content in the loop is relatively high from 12-17 mol%

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By :    Eddy Cooper – Agrium, Canada
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Q 3b.6:           How much of the significant efficiency gains do you attribute to simply replacing the aging converter catalyst? Can you break down your O.7 MMBtu/st gains among the various things you fixed and improved?
A 3b.6:           It is difficult to separate and quantify the improvements based on the new internals vs. the new catalyst. Another aspect is the fact that we had bypassing occurring in the packing gland at the outlet as well as some bypassing in the internal heat exchanger prior to changing out the internals.  We believe the bypassing in the packing gland at the cold-shot and outlet was occurring when the S-200 basket was initially installed. We found that a “retaining ring” was missing when we removed the old internals.  So we cannot really fairly compare Start-of-run conditions from the new catalyst and old catalyst. Another aspect of comparing the Start-of-run conditions of the previous catalyst and the new catalyst is we were not making methanol at the start-run with the previous catalyst and we were making methanol at the start-of-run with the new catalyst and that has an effect on the production rates. When we are making methanol our inlet inerts to the converter is about 5% higher than when we are not making methanol and of course that will have an effect on the converter performance.

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By :    G. K. Gautam – IFFCO Aonla Unit, India
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Q 3b.7:           Whether all glands / packing in S-200 during casale modification of internals were replaced by elasto seals?
A 3b.7:           Casale uses elastic seals for all the inaccessible (internal parts) of the cartridge.  Packing is still used on cartridge top cover and outlet pipe.

1 comment:

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