LYNCHBURG, VA — November 17, 2017
TRAX was contracted to examine the effects of installing a bypass damper and associated ductwork around the jet bubbling reactor (JBR) equipment of a coal fired power plant. Design was complicated by several factors:
- Physical space restrictions limited the size and configuration of the duct
- During a trip of the scrubber, furnace pressures had to remain negative
- Required placement of bypass damper and duct breachings created complex flow behavior that precluded the use of simple duct sizing calculations
TRAX found that using ProTRAX software for dynamic simulation, in combination with Computational Fluid Dynamics (CFD) software for modeling steady state flow conditions, provided a comprehensive solution to the problem. Assembling a CFD model allowed TRAX to evaluate the steady-state flow patterns and resulting pressure drops of different ductwork configurations. These values were then used in the ProTRAX model to evaluate whether a design would cause furnace pressure to go positive during a severe furnace transient event.
A 3D model of the JBR vessel, bypass duct, and stack inlet duct was created for use in a CFD analysis. The bypass ductwork was initially sized at 8 feet in diameter with a butterfly type damper near the bypass inlet. Flue gas flow entering the CFD model was estimated and the solution was calculated. The solution provided the exact pressure differential across the bypass for the specified flow rate. These values were input into ProTRAX as design parameters for the new bypass.
TRAX initialized the ProTRAX model at full load with the JBR bypass closed and triggered a dual booster fan trip. Following the fireball collapse, furnace pressure began to increase. In order to prevent the positive furnace pressure excursion, further iterations between the CFD and ProTRAX models were required. The sizing process was repeated until a duct diameter was found that prevented positive furnace pressure excursions; however, this duct size was not feasible due to size and weight constraints. TRAX recommended a 10 foot diameter duct, as it provided the best balance of reduced positive pressure excursions and size.
Combining the capabilities of ProTRAX and CFD software can provide economic benefits to many new and existing plant processes. CFD analysis of new equipment provides the in-depth operational data that can be used with ProTRAX models to simulate system-wide operations, which allows for detailed analysis of control strategies and expected system performance.
Peak performance of new or existing emissions control equipment such as FGD or SCR systems can also be realized through the use of CFD models. Prediction and optimization of reactant mixing and emissions reduction can be carried out without the need for extensive testing at the plant. CFD analysis can even be used to test bag house design to ensure even flow distribution and reduce the strain on individual filter bags. The design changes that result from the CFD analysis can then be fed back to ProTRAX models to show what impact the changes may have on system operations as a whole. This comprehensive approach to process simulation utilizing ProTRAX and CFD software offers many opportunities for clients to maximize process efficiency and profits.