Boiler Process Modelling and Simulation

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Boiler HRSG gas-path CFD study

Tetra Engineering provides a full-scope service for the modelling and operation analysis of all types of natural or forced circulation Power Boiler and HRSGs, including supercritical and once-through designs.  This can be integrated into a full plant model to incorporate the steam turbine and steam cycle balance of plant.

The level of detail can be adapted to focus on local effects (e.g. row-to-row temperature differences) and can be steady-state or time-dependent, the latter to model transients such as startups.  The state-of-the-art Power Plant Simulator and Designer™ (PPSD) software package developed by KED software is the primary tool for this work.  Frequent applications at Tetra Engineering include:

  • Calculating steam cycle efficiency (heat balance) according to ASME PTC or other codes
  • Determining natural circulation rates in support of FAC risk assessment
  • Generating metal temperature profiles for inputs to finite-element stress calculation
  • Assessing the impact of design changes or modification to original plant operating regime

Contact James Malloy (EMEA) This email address is being protected from spambots. You need JavaScript enabled to view it. or David Moelling (Americas) This email address is being protected from spambots. You need JavaScript enabled to view it. for more information about thermal simulations. 

 

Thermal Shock / Impingement Assessment

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Many combined cycle power plants have experienced thermal shock damage to bypass power piping, especially in the HP steam and Hot Reheat systems. Severe shocks occur when inadequate drainage exists and liquid water accumulates in bypass piping, for example during periods of operation when the bypass is closed or during shutdowns.   Startups where the bypass is opened then allows the accumulated liquid to be picked up and carried at high velocity downstream where it impacts on the internal surface at a change in piping direction, imparting a significant load and associated stress.  Low load operation is another means by which very high attemperator spray can fail to be absorbed by the steam and consequently come in contact (in liquid form) with the pipe wall.

T23 Tube Failure

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During the startup of the triple-pressure HRSGs, plant staff noticed steam coming from the stack and a discrepancy between feedwater and steam flows.  On shutting down the unit a T23 superheater tube was found with a complete circumferential failure.  The failed tube was removed and the bore was plugged with some difficulty due to poor access and the uncommon material.

Understanding variations in Flow-Accelerated Corrosion Wear Rates in HRSG Evaporator Tubes

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Very large differences in tube wall thinning rates by flow-accelerated corrosion (FAC), or in some cases fluid erosion, are observed in the low-pressure (LP) evaporator tubes of certain HRSG designs.  The tubes located near the duct wall and occasionally near the gaps between module bundles have more rapid thinning.  Tubes in a given row nominally should have very similar process conditions, both on the gas-side and on the waterside.  Different wall thinning rates mean that process conditions differ across the tube row. 

ASME B31.1 Covered Piping Systems' Mandatory Requirements

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Since 2007, the ASME B31.1 Power Piping Code has included mandatory requirements on the Operation and Maintenance (O&M) of Covered Piping Systems (CPS), previously called High-Energy Piping.  The main concern is that the safety of these systems is very dependent on good O&M, which justifies its inclusion in the Construction Code.  There is room for flexibility depending on individual circumstances but the responsibility is squarely laid on the Operating Company.

Impact of Startup Purge Credit on Combined Cycle Plant Operation

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Normal boiler and Heat Recovery Steam Generator Operation have required a complete purge of the boiler by fresh air before startup firing to remove potentially explosive fuels and other substances from the boiler/HRSG. For power plants in daily two-shift cycling (or more frequent starts) this not only adds time to the startup sequence but can impose significant thermal stresses on hot components exposed to cooler purge air. 

About Us

Established in 1988, Tetra Engineering has more than 25 years experience providing solutions to the power industry. We specialize in solutions for HRSGs, conventional boilers & steam-cycle balance of plant.

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Our Locations

Offices in: Connecticut, USA; Nice, France; Dubai, UAE.