Oxalate Line Descaling

Hydrochloric acid cleaning

Utrex Ltd
2 min readMay 18, 2016

The oxalate lines at an alumina refinery form part of a critical path for the precipitation component of a standard bayer circuit alumina refinery.

Lines don’t even have to be 100% restricted to have an impact on a given unit, restrictions have flow on effects. By the time inbound and outbound lines are blocked it will have a significant impact on the refinery.

The advantages of chemically cleaning the line as opposed to high pressure water or manual descaling were as follows:

  1. Reduced mechanical support requirements — scaffolding and fitting work required was significantly less
  2. Reduce timeline for cleaning
  3. No solid waste to remove

Our Process

The team utilised hydrochloric acid at the right concentration and circulated for four (4) hours.

Entry and exit blanks on the end of each of the common headers for each rotating oxalate filtration unit were opened and looped with temporary pressure, chemical and temperate rated hosing.

Before & After

Fig 1. — Oxalate line pre cleaning

As you can see from the before photo there was significant scaling prior to cleaning.

The line was restricted to approximately 30% capacity. This was impacting production in the unit significantly.

The pipe shown to the left is a 2" internal diameter line, with the piping butt-welded at 90 degrees. This made chemical cleaning the most viable cleaning option due to mechanical and access issues.

This entry point shown to the left was linked to other inlets via temporary hosing to create a chemical cleaning circuit.

Fig. 2 — Oxalate line post cleaning

Per Figure 2 to the left, the chemical cleaning result was successful.

The process flow capacity for the line was restored to 100% in the oxalate unit.

The unit was returned into service inside 48 hours achieving the result that the client was looking for.

Surface cleaning of some components of the unit was completed by another team of ours with high pressure water. This integrated approach to multidisciplinary industrial services is what Utrex promotes to all it’s clients to achieve the best result.

Contact us

Please get in touch with us at contact@utrexltd.com and we’ll be happy to come to your site and see if we can assist you with any chemical cleaning or industrial services requirements.