Q & A for Ammonia Reformer Operation and Optimisation Webinar

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AmmoniaKnowHow.com webinar on 25 November was received with great interest by 359 registered participants from over 50 countries leading to over 250 messages, almost 100 questions, and 25 live polls.

All answers to questions raised during the webinar are listed below under each video presentation.

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Case Study: Primary Reformer Tubes Failure due to Human Error

In this presentation will talk about a real incident that happened in an ammonia plant primary reformer and lessons learned.

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Answered by Venkat Pattabathula

Q: What is the impact of a high % of hydrogen on the reformer cone?

A: The question needs to be directed to ammonia mechanical SME, whereas I am ammonia process/operations SME. 

Q: How can we be sure that the furnace is uniformly heated by checking flue gas temperatures?

A: The furnace’s uniform heating is ensured by bringing burners in a pre-set pattern, as described in one of my presentation slides. Since there were not many flue gas Tis in the radiant section, it was not the right indication for the furnace’s uniform heating.

Q: Please explain the role of the reformer’s air registers and does it can cause a hot spot in the furnace?

A: Air registers are used to adjust combustion airflow to each burner, and please refer to John Zink’s combustion engineering manuals.  No, they don’t cause hot spots.

Q: Tube wall temperature measuring during startup is mandatory or not?

A: It is considered a best practice to check reformer tube wall temperatures during startup.

Q: Can you tell us in detail about temperature measurements with a pyrometer?

A: Please refer to other presentations of this webinar.

Q: If there was no N2 circulation, why they put too many burners?

A: They monitored reformer heat up based on process outlet and not flue gas temperatures in the tunnels.

Q: That was a very nice presentation. What do you mean by stagnant heating?

A: Stagnant heating means there was no flow through reformer tubes during the reformer heat up before steam introduction.

Q: How do you achieve proper air distribution to all those burners? It may be required if the air-fuel ratio on all burners is within a particular envelope.

A: During startup, the air-fuel ratio would be much higher than usual, which is not critical, like in normal operation. Nevertheless, one should adjust combustion airflow through the local air register to avoid the loss of flame with excess air.

Q: I was a little late in joining. Which plant the tubes failed?

A: Reformer tubes failed in an ammonia plant reformer in North America.

Q: What is the normal cold startup time of Primary Reformer?

A: 12-24 hrs, depending on reformer heat-up rates.

Q: What engineering controls implemented after this incident?

A: Please refer to the presentation, and the key one was: Installed an automatic shutdown system to protect against overheating during startup

Q: If the gas composition is often changing, then what do you recommend for TWT measurements?

A: Keep checking them daily, preferably during night shifts.

Q: We replaced refractory in secondary reformer and following this we are experiencing fouling in waste heat boiler and BFW exchanger which requires steaming every 3 weeks. How could we solve this problem?

A: I suspect the refractory material might not be a low silica type (high alumina) that you have installed. I suggest you check the silica content of both refractory and catalyst support media in the secondary reformer in the next outage. Replace it with the right material.

Q: What is the best procedure for measuring the TWT with a pyrometer – how frequently we should measure TWT every day or 2 days or one week?

A: Please follow the instructions of the supplier of pyrometer in measuring TWTs. I suggest you monitor TWT daily if possible.

Q: Given that the incident occurred a while ago (1998?) is the BMS trip that arose from the incident a standard feature on modern ammonia plants?

A: Yes, BMS is a standard feature in modern ammonia plants, and however, I am not sure every technology licensor was offering frontend N2 circulation, high flue gas, and process gas outlet temperature trips.

Q: My reformer stack temperature has increased from 132 to 145 C. What can be the possible causes for that. What are the steps to check whether there is any scaling on the convection section tubes?

A: It might be because of the coils’ fouling in the convection section, and some vendors could offer you on line cleaning of convection section coils.

Q: How much was the differential temperature between the flue gas temp and the process gas outlet temp when the failure occurred?  What much is the maximum?

A: It was about 1000 DegC.

Q: Were operators from this case study trained with an Operator Training Simulator? Since they can simulate startup, steady-state operation, and shutdown, they help to avoid problems derived from human error.

A: At the time of the incident, they didn’t have any OTS, and they got one after the incident. Nevertheless, one shouldn’t be complacent about OTS training alone, and operators should undergo periodical refresher training with bench top discussions as part of lessons learned exercise from industry incidents.

Q: “How often an operator check the physical condition of tubes inside the furnace and take tube temperature measurement?

A: At least every hour during startup and once every 4 hrs during normal operation.

Q: What is the philosophy for having a spare charge of catalyst for primary reformers.?”

A: No need to have a spare charge of reforming catalyst on site as it’s available from any of the 3 vendors for urgent use.

Q: I like to know the consequences of installing tubes without paying attention to hanger springs.

A: Potential bowing of tubes and ultimately resulting in tube failures over time.

Q: We lost process gas, process air, and lost steam production; what would be the radiant box’s possible effect? Does heat trapped and cause tube failure in the radiant section?

A: On total power failure and loss of feed & fuel gas to the reformer, I suggest you bring the reformer to a safe shutdown state by isolating fuel and feed gas and keep operating the ID/FD fans. Do not try restart in hot conditions without conducting complete checks around the reformer furnace.

Q: How to make sure the flame of the burner in good condition?

A: Please refer this to the suppliers of burners such as John Zink, Zeeco etc.

Q: How is the optimum ratio between the fuel and the combustion air of each burner?”

A: Please refer this to the suppliers of burners such as John Zink, Zeeco etc.

Q: What are the possible cause of outlet pigtail overheat, material Incoloy 800HT

A: Very high temperatures in reformer flue gas stream could damage the exotic materials too.

Q: Pigtail material composition, especially Ni content

A: We need to refer this to another mechanical SME as I ammonia process/operations SME.

Q: Some primary reformers include a trip for the high-temperature difference between primary reformer process temperature and flue gas temperature. What is the significance of this trip?

A: I am not sure about it, and I would recommend tripping the reformer on either of these conditions: a) process gas outlet high temperatures b) flue gas high temperature on a reliable voting system.

Q: Were the Operators’ procedure written such that instrument numbers were referenced or just descriptions of the instrument?

A: In this plant, all the instrument tag numbers were part of SOPs.

Q: What is the pigtail material condition

A: The outlet pigtails have failed (refer to presentation slides).

Q: During startup, we only heat up without any media inside the tubes?? Initially.

A: You have to pay much attention during heat up and monitor the startup such as flue gas and tube wall temperatures, number of burners online at each step, furnace inspection though peep doors for tube condition, etc. However, I suggest you modify the system to have frontend N2 circulation to prevent these incidents.

 

How to Improve the Radiant Efficiency of Your Primary Reformer?

In this presentation we will talk about Cetek coating technologies that improve the heater’s radiant efficiency and reduce fouling.

Answered by Vitaly Geraskin

Q: What is the impact of the ceramic coating on the  convection section of the primary reformer. Is there less heating going to the convection section?

A: Yes, high emissivity coating reduces the amount of heat going to the convection section and the stack. We evaluate each reformer before the project and provide the customer with the estimated benefits.

Q: What kind of surface preparation is required to apply this coating for old used refractory

A: We apply the coating ourselves and do all the surface prep needed.

Q: how is the coating mechanical properties? we usually going inside the furnace to inspect and doing maintenance, which is possibly hit the wall surface.

A: To damage the coating, you will need to damage the refractory.

Q: Does the effectiveness of the coating application depends on the initial refractory surface condition?

A: No

Q: this coating life will be affected by draft or not
A: No

Q: we are also facing dust from refractory during normal operation and it is accumulating on tubes wall.so is there any coating to improve refractory life

A: Yes, our coating can increase the life of refractory

Q: If we are already facing Issue of High TWT then how it will help us.in this way flue gas temperatures will decrease f=more

A: We need more information about the reformer to answer this question.

Q:  Data sheet for this coating material and the vendor name

A: IGS Cetek, We provide our customers with turn-key solutions.

Q: Any experience with this coating in flue gas duct?

A: We need more information about the problem you are facing

 

Orbital vs Manual Welding – striving for perfection!!

In this presentation we will talk about the benefits of automated welding for reformer pigtails versus manual welding.

Answered by Ben Cohen

Q: What about stress analysis after welding? After welding what about stress analysis

A: The weld profile has been checked with FEA that’s why we require a specific geometry of the fillet.

Q: How does the operator/machine certification work?

A: The welding systems are fully calibrated and the welders are qualified to ASME IX.

Q: How many welders or systems could you supply for a project?

A: We have supplied 12 full Orbital welding systems for a project and we had thirty qualified welders working  24/7.  12 days/12 nights extra guys to cover rest days.

Q: Does the system remove the welding fumes? what’s the power source for the machine?

A: The welding GTAW so it would not have an extraction system.  Our welder use Reactor light Air fed welding systems.  The power source is from Europe. 

Q: Any pipe size diameter constrains?

A: We have not had any issues obtaining equipment to carry out the projects we have undertaken so far.

Q: How quickly could you mobilise a team to carry out this type of work?

A: Depends on where the work is 1-2 weeks should be achievable.  Total systems and number of Welders required is a factor.

Q: How many of your automated welding machines work in parallel to save time?

A: 12 full Orbital welding system

Q: Would additional clearances be required on larger diameter outlet header pipe?

A: We have welded with a weld head that can rotate in a 45mm gap.

Q: If refractory accumulate on tubes welding joints will it effect tube welding because it is reflecting heat?

A: Material to be welded must be fully decontaminated.

Q: What is maximum diameter size for this automatic weld?

A: The range of weld heads for Reformer tube welding have a range of 8mm o/d – 168.3mm o/d.

Q: How do you manage to keep Argon inert gas availability inside the pigtail while welding from outside?

A: Soluble Damp materials and various purging tools.

Q: What clearance is required between the tubes? Examples were provided for welding tubes in the vertical orientation, can this be used for welding tubes in horizontal orientation?

A: We have welded with a weld head that can rotate in a 45mm gap.  Yes, we can complete butt welds and fillet welds in the horizontal position.

Q: If refractory accumulate on tubes welding joints will it affect tube welding

A: Material to be welded must be fully decontaminated.

Q: It is applicable to any typical reformer?

A: Yes, we are working with a number of different reformer systems.  Fillets leg lengths vary as do the pipe diameters.

Q: What is the job time and quality comparison between manual welding, and this automated welding?

A: Orbital is 2-3 times faster than manual.  Welds completed to the same welding parameters vary very little.  Manual welds depend on the skill of each welder.

Q: What is the percentage of defects in weld joint after adopting this technology?

A: Generally, less than 1%.  Machining of butt welds is critical; purging must be maintained as to ensure correct of Oxygen content.

Q: Any experiences in using RT and UT for Tube to Tubesheet weld? Please comment on the feasibility.

A: Langfields have completed a Nuclear contract with excess of 600 tube to tubeplate joints passing RT.  Do not think the joint geometry suits UT.  A NDE company may advise.

 

How to design and install a fully automated tube wall temperature (TWT) system to improve plant safety and reliability?

In this presentation we run through the benefits and design features of advanced reformer temperature monitoring solutions.

Answers to be uploaded once received. Please refer to the webinar video presentation for live answers.

 

How to Keep Your Fired Heater Efficient in-between Turnarounds

In this presentation we will talk about maintenance, including refractory repair, convection section cleaning, and SCR cleaning while the heater is in operation.

Answers to be uploaded once received. Please refer to the webinar video presentation for live answers.

 

Early Warning Solution of Ammonia Leaks in a Melamine Plant

In this presentation we will introduce a new remote monitoring technique that offers both the early leak detection and the situation assessment for the incident.

Answered by Rene Braun 

Q: How many sensor units will be required in a typical ammonia plant?

A: Each sensor unit detects gas at distances of up to 4 km away. So the number of sensor units is driven primarily by the requirements of the installation with regard to detection speed and spatial resolution. Often times a square kilometre can be covered by two sensor units.

Q: When does the wind speed start affecting the detection?

A: The scanfeldTM early warning solution can assess the entire gas cloud, even when the cloud travels over the plant. It tracks a moving cloud as it gets carried with the wind flow even changing direction and propagation speed. And it also monitors how the cloud is diluted until below detectability.

Q: Is one device capable to cover a whole plant (complex plant ammonia & urea & utility) or does each unit need a specific device

A: An installation of the scanfeldTM early warning solution is designed to cover both production units, storage and utility as well as guarding the fence. We provide a planning session to design the installation that specifically fits your needs.

Q: Can it differentiate between steam leak and hazardous gas leak?

A: Yes, we can. scanfeldTM performs it chemical analysis by means of FTIR spectroscopy that uses infrared light. Infrared radiation can travel even through fog and reveal the chemicals the air.

Q: Is it already in operation?

A: Yes we are installed as a solution provider for early warning of both flammable and toxic gases and especially monitoring major chemical parks.

Q: What’s the detectable limit for ammonia?

A: The detection limits for ammonia are in the low ppm region. Specific detection capabilities depend on the custom specific design of the installation.

Q: Can equipment be installed in explosive zones?

A: The design of the equipment allows positioning distant from ex-zones.

Q: Can we install it at height to look from top covering all area like CCTV

A: Yes, exactly. It moves continuously and can pan and tilt in all directions. Installation at high points is recommended. Our project development team will figure out the best installation points with you.

Q: How this camera cover a large area if obstacles like equipments come across?

A: Each sensor unit needs clear line of sight to the target gas cloud. The automated coordination of all sensor units allows coverage from all angles. Elevated installation points provide maximum overview.

Q: Is this equipped with multi-gas sensing detectors?

A: The power of FTIR spectroscopy is the chemical identification of a huge number of chemicals even in mixture. We display the chemicals separately or define custom-specific target gas libraries of gas mixtures.

 

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