The Client had severe issues with the installation of their 6 and 7 Power Boilers and requested engineering services to address these problems. The existing PB6 and PB7 combustion air systems had significant design issues and their Low NOx burner systems were not adequate for the boiler systems. Additionally, the existing PB6 and PB7 super heater sections suffered from heat affected areas due to repeated refractory failures. The original designer and installer of the system attempted to make corrections to the design several times but failed to make adequate corrections to the system. TAI corrected the poor design and installation attempted by prior engineers.

Significant vibration of the floor in the boiler building occurred as a result of the original installation configurations from the fans. The Client’s goal was to increase reliability and minimize issues and provide a stable system between required maintenance.

Services required:

• Detailed engineering design and construction services for the rebuild of the PB6 and PB7 boilers;
• Development of battery limit services for the RB3 natural gas load burners installation;
• Detailed engineering for required sub-systems; and
• Evaluation and corrective action for Superheater Deformations which were resulting in mechanical issues and separation of internal refractory.

TAI supplied a Senior Project Manager who was experienced with process mechanical power-related projects and was responsible for the project scope, schedule, budget, quality of documentation and the construction support.

TAI engineered several solutions to this project, including:

• Installed a new FD fan system with VIV damper, inlet damper, associated inlet and outlet ducting, inlet air flow measurement device and other associated instrumentation to provide combustion air to each respective boiler system (PB6 and PB7).
• TAI designed a new larger concrete pedestal foundation for the new FD Fans, incorporating equipment access into the design.
• Steam coil air heaters located in the combustion air system inlet duct were taken out of service during the demolition portion of the construction project and relocated and repurposed for building heating.
• Steam feeds to Steam coil air heaters (SCAH’s) were modified to suit new locations. Revised steam piping was stress analyzed per applicable code requirements.
• TAI modeled the existing super heaters and internal coils to evaluate the stresses and deformations. TAI utilized the model to design a new support system (that included spring supports) to minimize the superheater section stresses and deformations during heat-up, cool-down, and load changes. A new wall and roof casing panels (PB6 only, reuse PB7), including a new refractory system, was designed and installed.
• Refractory design was by a third party but TAI accounted for the weight of the new material.
• Wall and roof casing panels incorporated weight of new heavier refractory material into the design.
• The existing PB7 steam circulation through the super heaters was changed to address temperatures that exceeded the long-term super heater tube metal temperatures that were currently measured. The existing external steam piping header sources (secondary super heater only) was rerouted to allow for the coolest steam to contact the hottest flue gas. All high-pressure steam piping was modeled and stress analyzed in accordance with all applicable codes.
• Natural gas load burners were installed in the chemical recovery boiler (RB3) to allow for firing at maximum conditions for when an upset occurs in the plant. Battery limit service connections (natural gas, compressed air, vent piping) was provided to (and in some cases from) the Load burner vendor’s equipment.
• Performed construction administration working with Owner’s selected mechanical and structural contractors to ensure design was implemented in accordance with approved drawings.

TAI supported this project by providing comprehensive project management, engineering, and design for the development of detailed design documents. Our mutli-disciplinary team achieved success working on the stress and structural aspects of the Superheater and the FD fan foundation re-design, eliminating the vibrations from the FD fans on the fan deck. The deformation and “hot spots” on the superheaters and vibrations of the floor in the boiler house building were essentially eliminated due to the modifications that were performed. Modifications and installations were made on time. The Client reports that the systems have been operating normally since TAI’s modification designs and recommendations were implemented.