Analysis of temperature and stress distribution of superheater tubes after attemperation or sootblower activation

• The CFD simulation was used to calculate 3D steam and tube wall temperature distributions in the platen superheater.
• The CFD results can be used in design of superheaters made of tubes with complex cross-section.
• The CFD analysis enables the proper selection of the steel grade.
• The transient temperature and stress distributions were calculated using Finite Volume Method.
• The detailed analysis prevents superheater tubes from excessive stresses during sootblower or attemperator activation.

Superheaters are characterized by high metal temperatures due to higher steam temperature and low heat transfer coefficients on the tube inner surfaces. Superheaters have especially difficult operating conditions, particularly during attemperator and sootblower activations, when temperature and steam flow rate as well as tube wall temperature change with time. A detailed thermo-mechanical analysis of the superheater tubes makes it possible to identify the cause of premature high-temperature failures and aids greatly in the changes in tubing arrangement and improving start-up technology. This paper presents a thermal and strength analysis of a tube “double omega”, used in the steam superheaters in CFB boilers.