GBH Enterprises, Ltd.

Naphtha Steam Reforming Catalyst
Reduction by NH3 Cracking

Process Information Disclaimer
Informat...
Naphtha Steam Reforming Catalyst Reduction by NH3 Cracking
Scope
This procedure applies to the in situ reduction of VULCAN...
2. Heat the reformer to a measured inlet temperature in the range 475 to 500°C
(887-932°F) and a measured exit temperature...
9. If no hydrogen is detected after 2 hours and the ammonia levels in the
process condensate remain high (>>100 ppmw), the...
Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutd...
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Naphtha Steam Reforming Catalyst Reduction by NH3 Cracking

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Procedure for Naphtha Steam Reforming Catalyst Reduction by NH3 Cracking

Scope
This procedure applies to the in situ reduction of VULCAN Series steam reforming catalysts using ammonia cracking to form hydrogen over the catalyst in the steam reformer. This procedure covers plants with a dry gas circulation loop for reduction. The procedure is likely to be applied to plants using only heavier feeds (e.g.: LPG and/or naphtha) and some combination of VULCAN Series catalysts.

Introduction
A small number of steam reforming plants do not have an available source of the commonly used reducing media (e.g.: hydrogen, hydrogen-rich off-gas, natural gas). These plants will usually operate on LPG and/or naphtha feed only where cracking of this hydrocarbon is not usually advised for reduction of the steam reforming catalyst. In such circumstances, the plant may be designed to use the installed steam reforming catalyst to crack ammonia to provide hydrogen for the reformer catalyst reduction....

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Transcript of "Naphtha Steam Reforming Catalyst Reduction by NH3 Cracking"

  1. 1. GBH Enterprises, Ltd. Naphtha Steam Reforming Catalyst Reduction by NH3 Cracking Process Information Disclaimer Information contained in this publication or as otherwise supplied to Users is believed to be accurate and correct at time of going to press, and is given in good faith, but it is for the User to satisfy itself of the suitability of the Product for its own particular purpose. GBHE gives no warranty as to the fitness of the Product for any particular purpose and any implied warranty or condition (statutory or otherwise) is excluded except to the extent that exclusion is prevented by law. GBHE accepts no liability for loss, damage or personnel injury caused or resulting from reliance on this information. Freedom under Patent, Copyright and Designs cannot be assumed. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  2. 2. Naphtha Steam Reforming Catalyst Reduction by NH3 Cracking Scope This procedure applies to the in situ reduction of VULCAN Series steam reforming catalysts using ammonia cracking to form hydrogen over the catalyst in the steam reformer. This procedure covers plants with a dry gas circulation loop for reduction. The procedure is likely to be applied to plants using only heavier feeds (e.g.: LPG and/or naphtha) and some combination of VULCAN Series catalysts. Introduction A small number of steam reforming plants do not have an available source of the commonly used reducing media (e.g.: hydrogen, hydrogen-rich off-gas, natural gas). These plants will usually operate on LPG and/or naphtha feed only where cracking of this hydrocarbon is not usually advised for reduction of the steam reforming catalyst. In such circumstances, the plant may be designed to use the installed steam reforming catalyst to crack ammonia to provide hydrogen for the reformer catalyst reduction. This may be on a once through basis or with gas recycle through a circulating loop. By control of the steam to ammonia ratio and reformer exit temperature, oxidized catalyst cracks ammonia to generate hydrogen which then affects a degree of catalyst reduction. Once some reduced nickel is present, ammonia cracking becomes efficient and the period in which ammonia is observed in the process condensate is kept to a minimum. Procedure 1. Ensure the primary reformer catalyst is heated in a nitrogen flow to above the dew point of the process stream. Once this temperature is exceeded by at least 50°C (90°F), continue heating with process steam. The system pressure should be in the usual range for the reformer start-up circulation loop (typically 10 – 15 bara). Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  3. 3. 2. Heat the reformer to a measured inlet temperature in the range 475 to 500°C (887-932°F) and a measured exit temperature of 780 to 800°C (14361472°F). If the plant design does not allow the inlet temperature to attain this level, then the inlet temperature should be as high as possible within the constraints of the plant. Temperature losses to the point of exit temperature measurement are usual at this low load of operation and the actual tube exit temperature will be higher than these values. Regular (1/2 hourly) inspections, ideally with an accurate IR pyrometer, of the reformer are necessary to check for possible overheating. 3. At the above temperatures, control the steam flow through the primary reformer insofar as this is possible to remain within tube skin temperature limits and to satisfy the ratio of steam to ammonia as specified in (5) 4. Maintain a nitrogen gas circulation rate of 40-60 Nm3/hr per reformer tube. 5. Inject ammonia at an initial rate to satisfy a steam to ammonia molar ratio of an absolute minimum of 20:1. This will be sufficient to carry-out the catalyst reduction, but hydrogen will take 1-2 hours to be detected in the recycle gases and ammonia in the condensate will be at high levels (>>100 ppmw) for this period also. To minimize the time to produce hydrogen and limit the amount of high ammonia concentration in the condensate, lower molar ratios of steam to ammonia should be targeted in the range 14:1 to 9:1. 6. Process condensate containing ammonia will need proper attention. Initial levels of ammonia could exceed 1000 ppmw, but will reduce quickly to <100 ppmw (typically 30-70 ppmw) once cracking occurs over the reforming catalyst 7. Maintain continuous injection at the required rate for at least one (1) hour. Monitor the progress of ammonia cracking by observation of process conditions (increasing loop pressure; dry gas circulation rate) and analysis. Adjust the rate based on the analytical results. 8. Take samples for analysis of the re-circulating gas for ammonia and hydrogen and of the process condensate for ammonia every 30 minutes over the first two hours of ammonia injection. Thereafter, reduce the frequency to every 60 minutes for as long as necessary. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  4. 4. 9. If no hydrogen is detected after 2 hours and the ammonia levels in the process condensate remain high (>>100 ppmw), then the molar ratio of ammonia to steam is possibly incorrect and/or the reforming temperature is low. 10. Once hydrogen is measured, the H2O/H2 molar ratio should be recorded (from a combination of analysis and calculation of the amount injected and cracked ammonia). The target point is when the H2O/H2 molar ratio enters the target reduction range of 6:1 – 8:1. The molar ratio may be allowed to go as low as 4:1 without cause for concern in terms of the catalysts within the loop. 11. Once the H2O/H2 molar ratio is in the range 6:1 – 8:1, stop ammonia injection. Continue to analyze at 60-minute intervals and calculate the H2O/H2 molar ratio in the loop. Hydrogen will be consumed slowly as the reduction proceeds. As the H2O/H2 ratio rises towards the top of the reducing range (H2O/H2 molar ratio = 8:1), inject a slug of ammonia to adjust the H2O/H2 molar ratio in the loop to about 6:1. 12. Maintain reducing conditions (H2O/H2 molar ratio in the range 6:1 – 8:1) for the following times depending on the recent shutdown history of the catalyst. See Table 1. 13. Following this, introduce hydrocarbon feed as described in the Operating Manual for VULCAN Series Naphtha Steam Reforming Catalysts. Table 1 – Catalyst Reduction Times Catalyst Steaming Period (Hours) <3 3-8 >8 Fresh Catalyst Charge Period of Reduction (Hours) No reduction required 6 hours of reduction 12 hours of reduction 18 hours of reduction Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  5. 5. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com

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