ANC CONTROL

Experiment 1: Minimum amount of lime input in two reactors

Introduction

In the first experiment of Spring 2010 team, the goal was to evaluate the lime feeder's performance with respect to its effluent pH with a minimum lime input based on theoretical calculations. This is the mass of lime which would dissolve in 12 hours given the flow rate and the calcium hydroxide solubility constant (equation 1.1). As can be seen in equation 1.2, the theoretical lime requirement is simply based on what could dissolve in twelve hours, and didn't take into account other factors which limit how much of the available lime will actually dissolve.

Procedure

The team basically used the same procedure described in the materials and methods section, although the lime is now fed through a vertical tube.

So that the experiment could be compared with the last experiment carried out by the Fall 2009 team (Experiment 3, Trial 4), the Spring 2010 team used the same flow rate, which was 40mL/min in both reactors, and a lime mass of 8gm based on the solubility calculations (figure 1.1). One important change was that the lime in this experiment was fed dry, not mixed with water as a slurry. This may affect the particle size distribution, which is discussed in the hypotheses section.

Results and Conclusion

From the experiment data shown in figure 1.2: the A1 reactor could barely go above 12 and the A2 reactor maintained a pH over 12 for just over 2 hours. Compared to Trial 4, which the previous team used fine hydrated lime instead of powdered form in this run, the comparison parameter--lime input, could be a very important factor and further discussion is shown in (kinetic hypothesis). The experiment also showed that the A2 reactor could create a much better suspension than A1, which means its new geometry reaches our expectation, but the 40mL/min flow rate is far from the ideal velocity to get the best suspension. By kept changing the up-flow and observing the suspension in A2 reactor, the team assumed the optimum flow rate was 120mL/min, which around this level best suspension could be acquired in A2 reactor.