Fly ash erosion (FAE) control requires a reduction in fly ash loading and/or gas velocities in areas with serious FAE. * Flow reduction is accomplish with various types of flow modification baffles: expanded metal screens (EMS), perforated plates (PP), solid baffles (SB), and turning vanes or ladder vanes.
Due to centrifugal separation, fly ash particulate loading can be unevenly distributed throughout the convective pass. Some baffle designs can be used to change the trajectory of ash particles and reduce above average particulate loading across a heat exchanger inlet. FAE is directly proportional to local particulate loading.
Most baffle designs are selected to reduce above average flow to design levels or to increase low flow zones to design levels. Expanded metal screens and perforated plate baffles are typically used. They can be installed horizontally, vertically , angled or as curved sections. Occasionally, turning vanes or ladder vanes are appropriate where sharp turns cause flow separation to one side of the pass.
Baffle designs and fabrication are fairly simple for temperatures regions below 1200°F. Materials are readily available and code welding and/or heavy structural supports are seldom required. Connections to pressure parts are mechanical with minimum weld attachments.
* See Erosion Fundamentals for further explanation.
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