Mechanism And Influnce Study On Hydrothermal Reaction To Decrease Sulfur From External Treatment Slag

At present, the enrichment of sulfur arouses during the recycling of the refining slag. Thecontent of the sulfur in the slag can be removed by the leaching method efficiently. By studyingthe mechanism and the effect factors of the leaching desulfuration process, we draw theconclusion that the sulfur element is easier be removed under high temperature and highpressure in basic fluid. The slag is expected to be used for more times after this desulfuration.The Eh-PH diagrams of CaS-H₂O system under different conditions are drawn in thisarticle according to the thermodynamic calculation. The result shows that the leaching reactionof CaS transfer into HS-and Ca²⁺hydronium can occur spontaneously. The progress of HS-togenerate S²⁺and Ca²⁺to form Ca（OH）₂are improved with the increased temperature. Besides,the stable area of Ca（OH）₂expanded and the dissipation of Ca is reduced at a higherconcentration. By study the thermodynamic analysis of the leaching desulfuration process andthe Eh-PH diagrams of CaS-H₂O system, we draw the conclusion that Ca²⁺and OH-generatewhen CaO dissolved in water, which is benefit to the leaching process proceeding to the highbasicity condition and the Ca dissipation reduced. Because of the existence of Al₂O₃, newproducts of the leaching process would be generated from Al³⁺、 Al（OH）₃and Al（OH）₄^-.Therefore, it is conducive to sulfur dissolved into water in the form of S^2-under hightemperature and high basicity while the dissipation of Ca reduced.We studied the kinetics of the leaching desulfuration process under high temperature andhigh pressure. The effect of temperature on the desulfuration rate is investigated during theleaching experiments and we also defined the kinetics model of the process as unreacted corecontraction model. According to the slag desulfuration rate in accordance with the X in kineticsequation1-2x/3-（1-x）^2/3kt controlled by diffusion, it can preliminary decided that thecontrolling step of the leaching desulfuzation reaction rate is the diffusion management. Theapparent activation energy of the reaction is23.314KJ/mol, the controlling step is blendingcontrol, and in which the diffusion control plays the leading role.Finally, the orthogonal experiment of L₉（₃⁴） based on the theory analysis was carryed outto study the influence mechanism of the leaching desulfuration process, the effect of leachingtemperature, the leaching time, the ratio of solid and liquid and initial pH on the slagdesulfuration. It shows that the initial pH value, followed by the leaching temperature are themain influence factors. The optimum desulfuration condition described as follows: the volumeratio of solid against liquid is1:7while the leaching process persist for45min at150℃, and theinitial pH value of liquid is13.5. Under this condition, the desulfurization can reach a goodresult about42.6%.