ANC CONTROL

ACID BACKWASH

OBJECTIVE

Find an easy way to wash the apparatus once the tubes become opaque with lime residue. The tubes are very long and removing lime stuck on the walls is a difficult task. The team did a trial using sulfuric acid (2 M), running it continuously for several hours. The team expected the acid to dissolve the lime coating.

PROCEDURE

1. Prepare a solution of sulfuric acid 2M.
2. Place it in a bucket. The bucket is plugged to the water inlet and receives water from the effluent making a closed circuit.
3. Leave the solution running until the lime gets dissolved and the tubes looks clear.
4. Check the pH of the water through a pH probe, making sure that the acid was not neutralized by residual lime.

RESULTS

After two hours of the running, the team found a leaking in one of the ensemble joins. All pieces were glued with silicone which was melted by the acid. As a result, the apparatus was disassembled completely and glued again using PVC glue. Despite it is supposed that the glue won't be melted with acid, the method was not employed again. Instead of sulfuric acid, the team washed all pipes with common bathroom cleaner, following a suggestion from the workshop. This proved faster, easier, and more effective. In the future we will use the bathroom cleaner whenever visibility is obscured by the lime residue.