MechChem Africa

MechChem Africa’s Peter Middleton talks to Multotec process engineer Carien Spagnuolo about the first commercial installation in Africa of the continuous ion exchange desalination solution, DeSALx®, which Multotec is introducing to the region as the local partner for Australia-based Clean TeQ Water.

1 Carien smallFollowing the introduction of continuous ionic filtration (CIF)® and its dual stage big brother for desalination, DeSALx®, Multotec, Clean TeQ’s regional partner for Africa, is currently installing its first commercial water treatment plant to use this technology.

“This is good news. We are now busy implementing our first-ever wastewater treatment plant to use the DeSALx ion exchange water purification process,” says Spagnuolo. “In conjunction with other water treatment technologies, this project will apply continuous ion exchange technology at an antimony roaster in the Middle East. Both the complexity of the treatment requirements and the harsh environment offer a rigorous testing opportunity for our technology,” she tells MechChem Africa.

“Antimony is a very interesting mineral. It has long been used for the lead antimony plates in lead-acid batteries and to improve the properties of lead-tin alloys, but it is increasingly critical for the manufacturing of modern micro-electronic components,” she tells MechChem Africa.

Antimony (Sb) is an element that is mined as a sulphide called stibnite (Sb2S3). Antimony roasting involves reducing this sulphide to produce metallic antimony, a process that also produces dangerous off gases that have to be scrubbed to prevent them from polluting the atmosphere.

“This project involves cleaning the wastewater from the scrubbers and the cooling tower blowdown. For the towers, because the cooling water is recycled, it becomes increasingly concentrated with dissolved salts. The DeSALx process has been widely used for purifying blowdown water, by taking the bleed off and removing the dissolved salts so that the water can continue to be used for efficient cooling,” Spagnuolo explains.

“The most important use for this treatment plant is to treat the scrubber wastewater, which is contaminated with antimony and arsenic, which are both heavy metals, as well as calcium ions, sulphates and sulphites,” she adds.

Four different feeds are coming in and are merged into our system, from two different scrubbers and from the cooling tower blowdown. “The scrubbers are used for flue gas desulphurisation, which removes the S02 before the off-gas is released to atmosphere. The S02 is the contaminant that causes acid rain and is removed by scrubbing with water. The wastewater produced is saturated with calcium (Ca2+) and sulphate (SO42-) ions. In addition to this, the scrubber wastewater for antimony roasters has dangerous antimony and arsenic contamination, which has to be removed and disposed of safely,” she says.

Multotec has taken the DeSALx technology and paired it with some conventional technologies and ended up with a highly efficient water recovery and desalination plant.

Describing the entire treatment process, she says that the first step involves traditional precipitation for the removal of the heavy metals – the antimony and the arsenic. “Essentially this is a ferric chloride dosing and clarification process that produces a metal sludge in a settling tank. But this is only the pre-treatment stage of the full process,” she reassures.

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Contact MechChem Africa

Title: Editor
Name: Peter Middleton
Email: mechchemafrica@crown.co.za or peterm@crown.co.za
Phone: +27 11 622 4770
Fax: +27 11 615 6108

Title: Editor
Name: Glynnis Koch
Email: mechchemafrica@crown.co.za
Phone: +27 11 622 4770
Fax: +27 11 615 6108

Title: Advertising Manager
Name: Brenda Karathanasis
Email: brendak@crown.co.za
Phone: +27 11 622-4770
Fax: +27 11 615-6108

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