Relevant knowledge introduction of DTB crystallizer
Aug 13,2025
DTB crystallizer is a magma circulation crystallizer. The lower part of the device is connected with an elutriation column, which is equipped with a conduit and a cylindrical baffle. When the DTB crystallizer is in operation, the hot saturated solution is continuously added to the lower part of the circulation pipe, mixed with the mother liquor containing small crystals in the circulation pipe, and then pumped into the heater. The heated solution flows into the crystallizer near the bottom of the conduit and is sent to the liquid surface along the conduit by a slowly rotating propeller. The solution evaporates and cools on the liquid surface to reach supersaturation. Some solutes deposit on the surface of suspended particles, leading to crystal growth.
There is also a precipitation zone around the annular baffle of the DTB crystallizer. Large particles settle in the settling zone, while small particles enter the circulation pipe with the mother liquor and are heated and dissolved. The crystals enter the elutriation column at the bottom of the DTB crystallizer. In order to make the particle size of the crystallized product as uniform as possible, part of the mother liquor in the precipitation zone is added to the bottom of the elutriation tower, and the DTB crystallizer is classified by hydraulic force, so that small particles return to the crystallizer with the precipitate. The crystals are discharged from the lower part of the elutriation column.
In order to ensure that the crystallizer has good thermal conductivity, sufficient wear resistance, mechanical strength and hardness to prolong its service life, the inner wall material of the DTB crystallizer mainly adopts copper-based alloys. Commonly used ones include copper and copper-silver alloys (with a silver content of 0.07% - 0.1%), phosphorus-deoxidized copper, copper-beryllium alloys, chromium-zirconium-copper alloys, etc. The main purpose of using copper-based alloys is to increase the recrystallization temperature of the DTB crystallizer, thereby improving its hardness and strength at high temperatures and prolonging the service life of the inner wall. To further improve the wear resistance and smoothness of the inner wall and reduce the drawing resistance, some DTB crystallizers are plated on the surface of the copper wall. Usually, there are three layers: chromium or nickel, tungsten, iron and nickel, nickel-phosphorus alloy and chromium plating.
In order to prevent the molten steel from sticking to the inner wall of the DTB crystallizer during condensation, reduce the frictional resistance during casting, improve the surface quality of the cast billet, and prolong the service life of the crystallizer, it is necessary to lubricate the crystallizer wall during production. For lubrication, liquid lubricants or mold fluxes with a boiling point higher than the temperature of the inner wall of the crystallizer (about 200℃) are used. During the vibration process of the DTB crystallizer, they are continuously brought into the inner wall of the molten steel and exposed to the molten steel or billet. An oil-gas film or slag film is formed between the mold shell and the inner wall of the crystallizer to lubricate the inner wall.
