The Effect Of Additives On The Crystallization Process Of Calcium Sulfate

In chemical industry and energy production, scale is a long-standing and actual difficult problem. In most cases, scale is mainly composed of carbonates, sulfates and phosphates. Chemical scale treatment agents affect the nucleation and crystal growth caused 2+ by irons (Ca ,CO32,SO42,etc.)~11. They include scale inhibitors and scale removing agents, typical scale inhibitors are organic polyphosphates, inorganic polyphosphates, polyacrylic acids, polycarboxylic acids, polyacrylamids and polyamino acids. Many other inorganic irons such as Fe3~,Fe2~,Mg2~ can inhibit the growth of CaCO3 and CaSO4 effectively; Typical scale removing agents include EDTA and hydrochloric acid , etc. This experiment studied mainly on the phenomenon of nucleation and crystal growth of CaSO42H20 in the supersaturating solution by measuring nucleation induction time and crystal growth rate, the effect on it by various inorganic substances as additives were also studied. The results suggest that the relation of nucleation induction time and the initial concentration of Ca2~ in the solution conforms to Nielsen-Christiansen nucleation equation: K=C0~?t CaSQ42H20 crystal growth is controlled by surface reaction, which is also size dependent; MgCI2 and Cd(NO)3 can inhibit the nucleation and crystal growth of CaSO42H20 effectively, their best dontent is 167mg/kg and 250mg/kg, phosphates are more effective, however, 334mg/kg CuC12 and 1000mg/kg K3Fe(CN)6 have comparably strong promotion effect. It is possible to use these additives for inhibiting scale or making it deposit fully in the phase of solution pretreatment, 3 天泽轻工业学院则十学位论文so as to attain the purpose of preventing scale in the key procedures．...