Study On Pellet Preparation Of Novel Silicothermic Process

Magnesium and its alloy have numerous unique properties, which are widely applied. The silicon thermal process is one of the major methods to produce magnesium. Based on the large number of domestic and foreign literatures on silicon thermal process, this article proposed a new method that dolomite was made into the pellets first, and then was calcined to prepared the pellets with higher reactivity and stability. And this process is useful to improve resource utilization and to reduce energy consumption. Based on this new consideration, decomposition reaction thermodynamics of carbonate and dolomite pellets process were researched.(1) Thermodynamic calculation indicated that as the temperature increasing, the standard Gibbs energy and the enthalpy of the reaction gradually reduced; and as the CO2 partial pressure during the reaction gradually reducing, the temperature decreased. Predominance area diagrams show that in the calcination temperature and calcination atmosphere, the MgO and CaO produced by dolomite decomposition can stably exist.(2) The research of pelletizing by adding different binders to dolomite indicated that the pellets added composite binder G were better than those added organic binder D and water in the aspects of particle size and compressive strength and fall strength. The fall strength of pellets added composite binder G was between 2.63/0.5m and compressive strength was 76.2N.(3) The pellets density detection of dolomite added composite binder G showed that the volume density and bulk density of pellets increased with the increase of the additive content, but decreased with the increase of pellets diameter.(4) The research of dolomite pellets calcination mechanism and calcination conditions showed that subsection calcining system should be used to calcine dolomite prefabricated pellets, and the optimal calcination condition was that heating up to heating to 1073K by lOK/min, insulating for 0.5h, and then heating up to 1273K by lOK/min, insulating for 0.5h.(5) The fall strength of pellets after being calcined changed slightly. Fall strength of sintered pellets was between 2.2/0.5m and 2.5/0.5m, and its compressive strength was between 45N and 56N. The composite binder G enabled the pellets to be calcined fast, which had a low powder rate and good product quality.(6) The burning rate of the pellets reached 39% which reached the theoretical loss rate when the pellets were calcined and preserved for 1 h using calcined system proposed in this article.(7) Using the prefabricated pellets process determined by this experiment, the reduction rate of ripe pellets obtained on the optimal calcination conditions was higher that of conventional process. The reduction rate of 1h was significantly higher than that of conventional press briquetting process after calcining dolomite.