ANC CONTROL
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Design 2010
INTRODUCTION
The Spring 2010 ANC Control team inherited the original apparatus used by the Fall 2009 team. The original design of the apparatus was giraffe-like in shape, with two 1" pipes connected at a 45 degree angle. See Figure 1.
Figure 1
In order to address the hypotheses listed on link to Drew's page here and also to increase the ease with which the lime is fed, our team redesigned the apparatus. We added a vertical column to the top half of the apparatus to allow for lime to simply be poured in. As the lime traveled down the vertical column, the particles would settle in the lower part of the apparatus and/or flow into the diagonal piece, but then settle out before leaving in the effluent.
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We attempted to correct this problem by sealing the top of the vertical column with a cap. This would result in a vacuum in the area about the water level and would allow the water in the column to remain at a constant height (see Figure 6). However, we were not able to fully seal the cap and having an open vertical column to pour lime directly into was part of the design's attractiveness.
Figure 6
We decided to alter the design instead by opening the very top of the diagonal column to atmospheric pressure. Doing so allowed for open channel flow in the tube and allowed the height of the water in the vertical column to remain constant, matching the height of the water level in the diagonal column. (See Figure 7)
Figure 7
Future design improvements
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Things that we would like to work on in the future would be changing the lower half of the apparatus. Throughout our experiments, we have determined that the lower vertical column is needed to keep the larger lime particles in suspension. Our experiments have shown that the smaller, finer lime particles travel up into the 2" diagonal column and are either suspended there, settle onto the lower diagonal, or travel up the upper diagonal and escape in the effluent. We would like to keep more of the lime mass suspended in the lower vertical column. One idea for achieving this would be to switch from a 1" column to a 2" column in the vertical section. (See Figure 8)
Figure 8
Another design change we are considering is the possibility of pumping the lime slurry up to the vertical column. This would make it more "user-friendly" as two of our members are not tall enough to feed the lime and thus, cannot run an experiment independently. Concerns associated with this method would be configuring Process Controller to run multiple pumps, differing flow rates for water verses lime slurry, when to pump which, and more. The pumping method also raises the issue that lime has to travel through so much tubing to reach the apparatus, providing it with a lot of surface area to settle on or coat. This will make it difficult to know exactly how much lime is actually making it into the apparatus.
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