HYDROSAL-XP ® is turning salt into gold
ON a beautiful sunny Saturday on 10 June 2017, I picked up BCI Minerals’ Mardie project manager Laurie Huck at the Eden au Lac hotel in Zurich.
We drove along the lake to Salt Partners offices in Erlenbach.
We spent the afternoon on the terrace overlooking the lake, speaking about salt crystallisation, harvesting, purification and membrane chloralkali technology.
During the dinner on the lake side we enjoyed the fish, the view and the sunset.
Back at the Eden au Lac, we said good bye.
Then, on 5 February 2018 after exchanging some 60 emails and various drafts, we signed a contract to supply the Salt Partners proprietary HYDROSAL-XP salt purification technology and provide project execution services to BCI Minerals.
HYDROSAL-XP capability
The main aim of the Mardie solar salt project is to supply 3 – 3.5 million tonnes of high purity salt to the chloralkali industry in the Asia-Pacific region.
Today, the chloralkali industry employs membrane cells for production of caustic soda and chlorine by electrolysis of sodium chloride solution.
In this process, impurities can severely damage the ion exchange membranes.
Calcium, magnesium and the ratio of calcium to magnesium in the salt are critical.
The HYDROSAL-XP process has the unique capability of selectively removing calcium and magnesium from the salt, thus favourably adjusting the calcium to magnesium ratio.
How HYDROSAL-XP works
Conventional salt washing processes discharge the washing brine to waste.
In the HYDROSAL-XP process, the purified salt and brine are separated in a centrifuge.
The brine from the centrifuge, the filtrate, is not sent to waste but collected in a filtrate vessel called Filtrex.
The filtrate contains fine salt particles. Adding water to the filtrate vessel and maintaining the mixture agitated sufficiently long, the salt fines are dissolved, creating pure saturated brine.
This brine is returned to the vessel from which the salt flows to the centrifuge.
In this vessel, called Hydrex or Hydroextractor, the brine flows upwards, in counter-current flow against the downwards moving salt.
In this counter-current process, called hydroextraction, all impurities that are more soluble than sodium chloride, i.e. magnesium chloride, magnesium sulphate, potassium chloride, sodium bromide, etc., are dissolved.
The sodium chloride is displaced from the saturated brine by common ion effect and crystallises on the salt.
Thus, an exceptionally efficient salt purification effect of 95 – 99 per cent is achieved and the processing losses are kept at a record minimum of 2 – 3 per cent.
On the schematic flowsheet, this section of the process is coloured blue.
Less soluble calcium sulphate is removed also in counter-current flow, but at higher velocities, with circulating brine by hydroclassification and elutriation.
This section of the process is coloured yellow.
By adjusting the brine velocities, the calcium to magnesium ratio is adjusted.
Salt Partners Ltd are independent consultants and engineering contractors, active in the field of salt production, processing and hypersaline biotechnology.
Salt Partners worldwide reputation is based on more than 45 years of experience gained in projects successfully implemented worldwide.
More information can be found at www.salt-partners.com.