Description of Mixers in Pipelines with axial flow impellers at Post Mixing

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This is a continuation of the Process Intensifier - Optimization with CFD: Part 1 paper.

Process Intensifiers with Dual Axial Impellers

LTA	HGA

Figure 3: Lightnin Line Blender with dual axial PBT impellers and a crucifix baffle. click on the picture for a bigger picture	Figure 4: Hayward Gordon In-Line Mixer with dual axial PBT impellers, a segmented ring baffle, and a criss-cross flow straightener. click on the picture for a bigger picture

Figures 3 and 4 show schematically the general concept of a Process Intensifier with axial flow impellers. The differences between the two models are:

Impeller locations
Impeller diameters
Flow orientation of the impellers
Baffle style and positions
Presence of flow straighteners
Inlet position of secondary fluids to be mixed in

The general flow pattern is from the left to right in these illustrations. A Z-divider plate with orifice does not exist in these tested models. That is not to say that the vendors would not offer this as an option (see Figures 3a and 4a).

LTA-with Z-plate	HGA-with Z-plate

Figure 3a: Lightnin Line Blender with dual axial PBT impellers and a Z-plate (not studied). click on the picture for a bigger picture	Figure 4a: Hayward Gordon In-Line Mixer with dual axial PBT impellers and a Z-plate (not studied). click on the picture for a bigger picture

Model LTA: The Lightnin Line Blender model (Figs. 3,5) has dual 3.5" (88.9 mm) axial 3-bladed PBT impellers with a blade width to impeller diameter ratio of w/D = 0.25. D/T is approximately 1/3. Although Lightnin would use hydrofoils, our model approximates the hydrofoil by using 3 blades at 30 degrees. Both impellers are down-pumpers. The distance of the centerline of each impeller to the top and bottom of the pipe is 2.5" (63.5 mm) and the spacing between the impellers is S = 5" (127 mm). There are two baffles. One baffle is shaped like a horseshoe and is on the wall of the pipe at the centerline of the shaft. It is continuous around the pipe except at the top, where it is open enough to allow insertion of the impellers. Another baffle runs the length of the pipe section to form a cross directly under the lower impeller. This is the pipe version of a standard crucifix baffle configuration. A secondary fluid to be mixed would enter the pipe 5 to 10 impeller diameters in front of the Line Blender through a T, depending on the flow rate.

Model HGA: The Hayward Gordon In-Line Mixer model (Figs. 4,5) has dual 5" (127 mm) axial 3-bladed PBT impellers with w/D = 0.25. D/T is approximately 1/2. Although Hayward Gordon would use hydrofoils, our model approximates the hydrofoil by using a pitched bladed turbine with 3 blades at 30 degrees. The distance of the centerline of each impeller to the top and bottom of the pipe is 3" (76 mm) and the spacing between the impellers is S = 4" (102 mm). The top impeller is a down-pumper, while the bottom impeller is an up-pumper. One baffle is a horseshoe baffle on the wall of the pipe at the centerline of the shaft. It is interrupted on the bottom by a 10-degree gap and at the top, where it is open enough to allow insertion of the impellers. A criss-cross flow straightener also precedes the impellers. A secondary fluid to be mixed would enter through a vertical pipe half way between the flow straighteners and the impeller blade tips.

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