Valuable technologies sometimes need some maturation and reinvigoration. This was also the case with the hydraulic washing column (HWC). TNO developed and validated the HWC technology for 20 years. To demonstrate scalability, two commercial plants were delivered during that period. The spin-out SoliQz is now marketing the HWC.

Valuable technologies sometimes need some maturation and reinvigoration. This was also the case with the hydraulic washing column (HWC). TNO developed and validated the HWC technology over a period of 20 yearse 20 years, TNO developed and validated the HWC technology. To demonstrate scalability, two commercial installations were delivered during that period. The spin-out SoliQz is now marketing the HWC.

Since late 2013, TNO has left this technology to the market completely independently through the spin-out SoliQz. The startup SoliQz is pulled by Nicolaas Viets and Dirk Verdoes, who was the leader of the HWC activities for many years at TNO.

Cooling an impure liquid mixture below its freezing point usually produces very pure crystals. The impurities remain in the liquid, also known as mother liquor. In the HWC, the crystals are separated from the mother liquor and washed in one column. The crystals and mother liquor enter the HWC at the top. The mother liquor leaves the HWC halfway through filters placed in filter pipes. The stopped crystals form a porous packed bed. A hydraulic pressure is created above the bed, which continuously transports the bed downwards. At the bottom of the HWC, the bed is broken up and the crystals melted.

This melt is the product of the HWC, a small part of which is returned to the bed as a washing liquid in countercurrent. The washing stops impurities from the mother liquor. As a result, the HWC product is very pure. The washing liquid does not leave HWC through the filters because it crystallises out on cold crystals. Washing with its own melt saves on the purchase and recovery of an external solvent. Due to the low temperature and high selectivity, the process is also very energy-friendly. In a working HWC, 3 zones can be distinguished: feed suspension, porous bed with mother liquor and clean crystals in contact with pure washing liquid.

SoliQz is now part of US appliance manufacturer Armstrong Chemtec, which supplies, among other things, industrial crystallisers. These can be perfectly paired with the SoliQz wash column to provide a complete purification process. However, the HWC can also be added to an existing crystallisation process , when the product from the crystalliser is not yet pure enough. You can visit SoliQz at PlantOne in Rotterdam. www.soliqz.com