Screen Worm Centrifuges Proves itself in Dewatering Crystalline Salts (April 2018)


Multotec Process Equipment’s custom designed version of the innovative Conturbex screen worm centrifuge has allowed a customer to almost double its production of dewatered sodium sulphate, while improving plant availability.

Gerrit du Plessis, product specialist in solid liquid separation at Multotec Process Equipment, explains that this design of centrifuge has a number of benefits in this application.

“The centrifuge rotates at a high speed of over 2 000 rpm to ensure effective dewatering, while the product is moved forward across the screen by a scroll mechanism,” says du Plessis. “This distributes the product evenly, which minimises the possibility of vibration due to uneven loads around the screen.”

He emphasises that vibrations can cause machine stresses if material gathers unevenly on the screen, potentially leading to mechanical failure and unplanned downtime.

“Another important feature is that the product has a relatively short residence time in the machine – only about two seconds – which allows it to absorb variations in feed rates,” he says. “This is significant because it can manage lower solids concentration streams, meaning fewer line blockages and lower energy consumption; this assists the continuity of the whole plant operation.”

Multotec worked closely with the customer to establish the operational and process parameters of the plant, to ensure that the Conturbex centrifuge machine would be fit for purpose.

“We also arranged for the customer to visit existing installations in the country where these units were operating in similar applications, as the screen worm unit is relatively new technology in this application,” says du Plessis. “This allowed the customer to gain the necessary confidence in the technology by talking to companies where it was already employed.”

So successful was the outcome of the new installation that the customer ordered two more of these machines for their plant.  Du Plessis highlights a further advantage in the design of the screen worm centrifuge, being the formation of thin layers of the solids on the screen.

“As it travels from the small diameter to the large diameter, the layer of solid matter remains loose and is constantly becoming thinner due to the increasing surface area of the screen,” he says. “This allows further dewatering without requiring high G-forces that would need greater energy inputs.”

The demanding conditions in the crystalline streams of these process plants, where there are high temperatures along with extremely corrosive and abrasive conditions, requires that Multotec utilise specialised, abrasion resistant materials to ensure long operational life and durability.

“Our capability in high quality design and precision engineering is also vital, as centrifuge technology is based on high-speed rotating equipment and fine tolerances,” he says.