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ANC CONTROL

TRIAL 1. TAP WATER

OVERVIEW

The team ran the experiment according with the design showed in experiment 3 wiki page. In order to run this experiment, the team had to calculate the upflow velocity required to maintain the lime in suspension and to achieve an effluent with pH of 12 units for 24 hours. According with the calculations, the optimal flow rate was 120 ml/min for an amount of lime of 80 grams.

INTRODUCTION

The experiment consisted in the injection of tap water with a flow rate of 120 ml/min; the required flow rate was regulated with a peristaltic pump controlled by the process controller software. The influent flew by the bottom of the apparatus through the top, were the effluent tube was installed. Before throw away the water, the pH was measured with a pH probe, the measures were collected in an automatic way, making use of the process controller software.

OBJECTIVES

• Evaluate the performance of the experiment 3 design.
• Determine the maximum time for which the pH at the effluent remains at 12.
• Determine some improvements for future experiments.

RESULTS

The apparatus worked well with the established upflow velocity. It was possible to observe the movement of particles. At the top of the apparatus, water looked clear but according with the pH sensor, it was saturated with base. A great amount of lime was captured on the middle of the apparatus; probably, the upflow velocity didn't allow the particles to reach the bottom of the apparatus again. However it is a desirable behavior because the lime was still in the apparatus, giving the protons needed by water.
The pH remained stable in 12 units just for 20 minutes. It was necessary to calibrate again the pH probe, to clean the apparatus and to review the calculations in order to determine the reason of the pH behavior. After the reviewing, the team decided to increase the amount of lime, because it was seen that not all the lime was on suspension.

Figure 1. pH vs time

CONCLUSIONS

• It was necessary to run one experiment recalculating the amount of lime.
• The design seems as expected and the movement of the particles was desirable. However, there was a cluster of particles that remains at the bottom and didn't dissolve.

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