Tube Wall Temperature Measurement On Steam Reformers - Best Practices

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Tube Wall Temperature Measurement On Steam Reformers - Best Practices
Temperature Measurement Techniques
Top – Fired Reformer
- Tube Temperature Measurement
- Background Temperature Measurement
Side – Fired and Terrace Wall Reformer
- Tube Temperature Measurement
- Background Temperature Measurement
Safety Considerations

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Tube Wall Temperature Measurement On Steam Reformers - Best Practices

  1. 1. GBH Enterprises, Ltd. Tube Wall Temperature Measurement On Steam Reformers Best Practices 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. Operating Manual Tube Wall Temperature Measurement It is very important to plant operation that the tube wall temperature readings are measured accurately and with a high degree of confidence. If in order to prevent premature tube failure due to overheating, the plant is run too conservatively, the full potential of the furnace will not be realized. On the other hand, if the reformer tubes are run to too high a maximum tube wall temperature, the furnace is likely to experience premature tube failures due to overheating, resulting in plant down-time and added expense of replacing the tubes and catalyst. It is very important that accurate tube wall temperature measurements are taken and a suitable correction method is employed to give the true tube wall temperature. This value can then be used to decide on a suitable plant rate and firing regime. Tube wall temperature measurements can also be used to ensure that the furnace is balanced with all tubes being run to the same exit conditions. There are several techniques available for tube wall temperature measurement, ranging from contact methods such as surface thermocouples and the Gold Cup pyrometer to the more common non-contact methods, which employ the use of an infrared, disappearing filament or laser pyrometer. GBH Enterprises has found over the years that a hand held optical pyrometer used in conjunction with a suitable correction method for background radiation results in accurate and trustworthy results. As with all non-contact temperature measurement techniques, the instrument relies on measuring the infrared radiation from the target. In practice, such pyrometers measure the total radiation from the target and the surrounding hotter surfaces. These instruments cannot differentiate between radiation emitted by or reflected from the target. They must therefore be corrected accordingly. The correction method used by GBH Enterprises is discussed in more detail in a subsequent section. For confident and sound temperature measurements, the following are recommended. 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. 1) The emissivity dial on the optical pyrometer should be set equal to 1.0 for the entire tube shoot. An emissivity correction factor of 0.85 will be employed manually for correction purposes. If the emissivity setting on the pyrometer is set at any value other than 1.0, then the measured temperature will be in excess of the true tube wall measurement thus inflating the measured temperature readings and imposing an artificial limit on the plant. 2) For each tube from which a temperature reading is taken suitable background measurements must also be made. These background readings should include all hotter surfaces visible to the measurement tube and likely to radiate to the optical pyrometer. Such surfaces include side and end wall refractory, furnace roof and flue gas extraction tunnels. 10 – 15 background temperature readings should be taken and used in the tube wall temperature correction. 3) The number of correction temperature readings taken should be scaled in such a way as to try and replicate reality. For the bottom temperature correction, readings for a top fired furnace more allowance should be made for the flue gas extraction tunnels than the end walls as these are going to contribute more background heat to the measured tube temperatures. This should be performed by taking more readings from the flue gas tunnels than the end walls. 4) Where the bottom peephole is below the tunnel tops, background readings should be taken from the tunnel walls and the furnace floor. If the peepholes are above the top of the tunnels then the temperature of the top of the tunnels should be measured; for every 4 measurements of the top of the tunnels, at least one should be taken from the furnace floor since this does contribute to the radiation measured by the pyrometer. 5) When taking any temperature readings either tube or background care should be taken to ensure that flame temperatures are not inadvertently picked up thus resulting in enhanced temperatures. 6) Where possible, temperature readings should be taken at 90º to the tube to minimize the path length and hence the radiation emitted by the flue gas. By using the shortest path length, the effect will be minimized. For all measurements the pyrometer should be placed as close to the peephole as possible to reduce the effects due to ambient surroundings. The peephole door should be open for the minimum possible period of time, thus ensuring that the temperature within the furnace will not have fallen during the tube shoot. 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. 7) Only one peephole should be open at any given time, thus preventing the possibly of a draft circulation effect occurring. 8) When any peephole is first opened it is recommended that any personnel stand to one side of the peephole for several seconds, thus ensuring that the furnace is running at a slightly negative pressure. It is possible for pockets of higher pressure to exist within the furnace, which may result in flames being emitted through a peephole. 9) Optical pyrometers have measuring angles of generally 33º. For typical furnace geometry at distances of greater than about 5m into a furnace a whole single tube cannot be seen, as it will be obscured by neighboring tubes. Radiation from these neighboring tubes will be picked-up by the instrument and mask the true temperature of the target tube. In addition, optical pyrometers have viewing angles of 7-9º. Therefore, at distances greater than 1m into the furnace more than one tube will be in the field of view. This creates problems for the operator of targeting the correct tube. At distances greater than 10m into the furnace, individual tubes are virtually impossible to target adequately. These distances should be borne in mind during any temperature shoot. 10) Temperature readings should be taken from all peepholes in order to get an accurate representation of the furnace operation. The distance for temperature readings should be minimized to reduce any sight path effects resulting from hotter furnace gases and also to avoid interference from neighboring tubes. On top fired furnaces, this requires that tube wall temperatures be measured from both ends of the furnace. 11) It is important that different people who take tube wall temperature measurements are fully trained so that all tube shoots are conducted in a systematic method. This allows for sensible and accurate comparisons between different people’s measurements. 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. Temperature Measurement Technique Top – Fired Reformer Figures 1 and 2 below will be used to explain the method used by GBH Enterprises for tube temperature measurement within a typical Top-Fired reformer. Figure 1 Tube temperature measurement Tube Temperature Measurement i. For each tube the temperature at the centre of the peephole height should be taken with the pyrometer held at 90º to the horizontal. Care should be taken to ensure that the pyrometer is held in a constant position for the entire tube shoot with all readings being recorded at a uniform level ii. Half the tube temperature readings should be taken from one end of the furnace, with the remainder being from the opposite end thus minimizing the length of radiation measurement. iii. This procedure should be repeated for all peephole levels, in order to ascertain the degree of balance within the furnace. 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
  6. 6. Background Temperature Measurement Figure 2 Background temperature measurement i. For each row of tube temperature measurements taken it is of extreme importance that an adequate number of suitable background (correction) temperature readings are also recorded. For both Row 1 and 3 it will be necessary to take 10 – 12 sidewall readings, half from either end of the furnace. It will also be necessary to take 3-4 end wall readings from the opposite end furnace peephole. All measurements should be taken at the same level as the tube temperature readings. ii. For top level peepholes it will be necessary to take some roof temperatures were possible, while for bottom level peepholes it is of vital importance that tunnel temperature readings are recorded as they contribute a considerable percentage to background radiation due to their very high operational temperature. The number of coffin temperatures measured and used in the correction technique should equal the number of sidewall correction readings. iii. For Row 2 where it is not possible to see the sidewalls corrections should be made using the adjacent tube rows 1 and 3 in the same way that the sidewall was used for the outer rows. The end wall, roof and tunnel temperature readings should be taken as described in ii. All the above recorded tube temperatures should be used in the correction method described later. 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
  7. 7. Side – Fired and Terrace Wall Reformer Figures 3 and 4 below will be used to explain the method used by GBH Enterprises for a typical Side fired and Terrace Wall reformer. Figure 3 Tube temperature measurements Tube Temperature Measurement iv. For each tube the temperature at the centre of the peephole height should be taken with the pyrometer held at 90º to the horizontal. Care should be taken to ensure that the pyrometer is held in a constant position for the entire tube shoot with all readings being recorded at a uniform level. v. If sidewall peepholes exist these should be used where possible to minimize any sight path effects, Figure 3 shows the method of tube temperature measurement to be used from the sidewall. If it is not possible to use the sidewall peepholes then the tube temperature survey should be carried out using the same method as that employed for the top-fired furnace. 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
  8. 8. Background Temperature Measurement Figure 4 iv. Background temperature measurements For each row of tube temperature measurements taken it is of extreme importance that an adequate number of suitable background (correction) temperature readings are also recorded. For end tubes it will be necessary to take 4-6 sidewall readings, half from either side of the furnace. It will also be necessary to take 6-8 end wall readings from the end side peepholes. All measurements should be taken from the same height as the tube temperature readings. v. For top level peepholes it will be necessary to take some roof temperatures were possible, while for bottom level peepholes it may be possible to take some floor temperature readings. vi. For Centre tubes where it is not possible to see the end walls, corrections should be made using the sidewall temperature readings, each sidewall temperature being measured from the opposite side peepholes as shown in Figure 4 above. All the above recorded tube temperatures should be used in the correction method described later. 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
  9. 9. Safety Considerations It is very important that all temperature measurements are carried out in the safest possible manner. Fire resistant clothing should be worn where possible and at a minimum gloves with a high resistance to heat. When making temperature measurements with the optical pyrometer normal cotton gloves are usually not adequate to prevent radiation burns to the hands and suitable heat resistant gloves should be utilized. During IR pyrometer surveys the use of green shaded IR furnace glasses is recommended to prevent any eye damage which may occur when viewing the inside of a reformer furnace for an extended period. These glasses also help when looking for hot banding since they make the hot bands stand out from the normal tubes. To prevent dehydration adequate supplies of water should be available on the furnace itself. For a large furnace regular breaks should be taken during the temperature shoot. For Foster Wheeler and Side fired reformers where 2 cells run in parallel, the time spent between the cells should be minimized as this area tends to be very confined with little or no breeze, hence increasing the possibility of thermal fatigue occurring. 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
  10. 10. 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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