The heart of the Crystalactor installation is the so-called pellet reactor, partially filled with a suitable seed material such as sand or minerals. Feed water is pumped in an upward direction at a superficial velocity of about 40-100 m/h, which depends on the type of application. To crystallize the target component(s) on the pellet bed, a driving force is created by a reagent dosage and chemical for pH-adjustment. By selecting the appropriate process conditions, co-crystallization of impurities is minimized and high-purity crystals (pellets) are obtained. The pellets grow and move towards the reactor bottom by gravity.
Research and practice have been demonstrating that maximizing the specific surface (m2 pellet surface per m3 reactor volume) near the reactor bottom is the key to a successful operation of pellet reactors. This requires an integrated approach and control of the hydraulic load, reagent dosing of base and supersaturation.
Intermittently, a quantity of the largest fluidized pellets is discharged from the reactor and fresh seeding material is added (picture 3). After atmospheric drying, readily handled pellets are obtained and the need for sludge dewatering, drying or hauling of sludge is eliminated. These pellets could be transported for reuse and/or commercial off-take, which could contribute positively to the financial balance.
Mr. Rietveld, professor of Drinking Water & Urban Water Cycle Technology of Delft University, explains in attached video the working of softening and crystallization.