Reducing Heat Loss in Steam Reformers - Infrared Thermal Scans
Steam Reforming is a process of converting methane and water molecules into predominantly hydrogen, carbon monoxide and carbon dioxide. These elements, collectively called synthesis gas, form the building blocks for the production of Methanol and Ammonia. In these petrochemical industries, this process occurs within catalyst tubes located in a gas fired Reforming Units. Significant heat is required (over 1000 degrees Celsius) to drive this endothermic reaction and reduce the quantity of inert compounds produced (namely methane slip).
Heat loss from a steam reformer in one petrochemical facility can result in millions of dollars in profit annually. Reduction of heat loss is therefore key in the conservation fuel and operating cost.One method of identifying heat loss is by the use of infrared thermal scans. Infrared thermal scans can be used to perform a thermal analysis of the reforming unit. This basically involves firing up the steam reformer to full rates (to ensure that the results obtained is applicable to normal operating conditions) and using a thermal imaging camera to take photos of the surface of the unit. Since heat loss usually occurs in areas between joints where the insulating material may not be as thick, focus should be placed in these areas.
High heat loss also occurs at the roof the reformer where the burners are situated and where the catalyst tubes enter the unit. The infrared thermal scans show the varying temperatures of the carbon steel metal sheets which are used to build the unit. Carbon steel temperatures in excess of 350 degrees Celsius are of concern since it represents areas where the internal insulation may have broken down increasing the heat transfer to the surface. At these temperatures, the rate of heat flow and loss is high and there is also the possibility of denaturing the carbon steel plates.
Thermal analysis can therefore be used as a preventative maintenance tool since it allows areas of high surface temperatures to be identified before potential failure occurs. Once identified, corrective steps can be taken to reduce the high temperatures and energy loss. These include repairing the refectory during outages or using a temporary fix such as reduce firing in the high heat area or using a steam lance on the affected zones.
Thermal analysis can also be used to determine the performance of the reformer burners. Poor burner performance results in temperature fluctuation of the catalyst tubes. This leads to excess methane slip which affects downstream processes and production of the facility. Infrared thermal scans of the burner tiles give a clear picture of the flame pattern of a particular burner and can be used to quickly identify plugged burner tips. By quickly identifying and correcting these operating problems, process plants will be able to reduce fuel consumption, energy cost and improve product quality.
by Mahindra Santoo
About the Author
Mahindra Santoo has worked in the Methanol Industry as a Process Engineer and used thermal analysis to identify and correct heat loss in Steam Reformers. The article submitted was based on work Mahindra did in this area. Since Mahindra would have to seek the permission of his past employers, the article was just a summary of what can be done and did not include actual results and case studies Mahindra has done on the Reformer.
Resources
http://www.irinfo.org/articles/2_1_2008_james.html - Inspection of Steam Reformers and Catalyst Tubes with Infrared Thermography
http://www.air-techinternational.com/diagnostic.html - Building Envelope Infrared Inspection & Testing Heat & Cooling Loss, Roof And Structural Defects Imaging, Subsurface Air, Heat & Water Leakage Detection Service
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New Infrared Thermal Imaging Systems
