Nooter/Eriksen was requested to evaluate the option of retrofitting a bypass stack with diverter into an existing waste heat boiler. The goals were to be able to install the equipment in the original system without impacting the exhaust back pressure and to allow for the future replacement of the waste heat boiler while utilizing the bypass stack.
Initially Nooter/Eriksen performed a CFD study of the original equipment utilizing field measured exhaust back pressure readings. Once a baseline was established, the new ductwork, diverter and bypass stack were added to the model for evaluation. The new model verified that the replacement equipment would not increase the back pressure during normal operation.
Challenges for the equipment design included utilizing an incomplete set of drawings for the original equipment created in 1971, installing the new equipment on the existing foundations, converting from refractory insulation to blanket insulation with a floating liner system, and using chrome-moly material for the bypass stack in order to avoid installing internal insulation in the stack. To accommodate the duct thermal movements (4) expansion joints were required. In addition to the ductwork, bypass stack, and diverter, Nooter/Eriksen also supplied a guillotine damper, blanking plate, and spring supports for the turbine plenum duct. The ductwork was trial fit at the fabrication facility prior to shipping to the owner’s facility in order to reduce time during field installation.