The quality OSLO evaporation crystallizer is also a crystallizer with a crystal slurry circulation. The lower part of the device is connected with an elutriation column, and the device is equipped with a guide tube and a cylindrical baffle. During operation, the hot saturated feed liquid is continuously added to the lower part of the circulation pipe, mixed with the mother liquor with small crystals in the circulation pipe, and then pumped to the heater.

The heated solution flows into the quality OSLO evaporation crystallizer near the bottom of the guide tube, and is sent to the liquid surface along the guide tube by the slowly rotating propeller. The solution evaporates and cools at the liquid surface to a supersaturated state, in which local solutes accumulate on the surface of the suspended particles, causing the crystals to grow. There is also a settling zone on the periphery of the annular baffle.

In the settling zone, the large particles settle, while the small particles enter the circulation pipe with the mother liquor and are dissolved by heating. The crystals were loaded into the elutriation column at the bottom of the quality OSLO evaporation crystallizer. In order to make the particle size of the crystallized product as uniform as possible, the local mother liquor from the sedimentation zone is added to the bottom of the elutriation column, and the action of hydraulic classification is used to make the small particles return to the crystallizer with the liquid flow, and the crystallized product is discharged from the lower part of the elutriation column.

In the crystal fluidized bed, the supersaturated solute in the solution accumulates on the surface of the suspended particles, causing the crystal to grow. The quality OSLO evaporation crystallizer performs hydraulic classification of the particles, the large particles are on the bottom, and the small particles are on the top, and the crystallized product with a relatively average particle size is discharged from the bottom of the fluidized bed. The fine particles in the fluidized bed flow into the circulation pipe with the mother liquor, and the tiny crystals in it are dissolved when reheated.