Research On Sulfur Transformation And Effect Behavior Of Additives In Coking Process Of High Sulfur Coal

Nowadays, with the shortage and continuously increasing price of coking coal, thecost for coking increases subsequently. Therefore, coking with high sulfur coal hasattracted a wide spread attention. However, the coke received after high sulfur coalcoking has high content of sulfur, causing a large increase of sulfur load in the blastfurnace production process and bring much inconvenience to metallurgy industrialproduction. Using additives to help sulfur transformation in the coking of high sulfurcoal can reduce the effects of high sulfur content on metallurgy industrial production.This paper first studies the machanism of sulfur transformation during the highsulfur coal coking process. The method of Fourier transform infrared spectroscopy（FTIR） and X-ray photoelectron spectroscopy （XPS） are used for testing Hun He coal（HHC） and the Tong Zi Coal （TZC） after HNO₃acidification and analyzing the existingforms as well as differences of the functional groups of C、S、O and N. The results of theexperiments show that the C funtional groups in both HHC and TZC are mainly C-Cand C-H while the COOH funtional groups in TZC are more than those in HHC.Therefore, the hydrophilicity of TZC is better than HHC. After comparing the Ofuntional groups in HHC and TZC, it is found that the C-O proportion in TZC isobviously larger than that in HHC. The O funtional groups in both TZC and HHC aremainly C-O, C=O and COOH. Because of the HNO₃acidification, the N funtionalgroups are mainly N-5and N-6and the NO₃is introduced. The S funtional groups inboth TZC and HHC are mainly thiophene and sulfone, but the proportions of oxysulfideand inorganic sulfur in HHC is larger.Then, the coking experiments were carried out using CaO、Fe₂O₃and La₂O₃asadditives. The effect of additives on metallurgical property of coke and the sulfurdistribution of coke were analyzed. The results show that additive has little impact oncoke breaking strength, wear strength of coke is deteriorated with CaO and Fe₂O₃addition and improved with La₂O₃. Coke reactivity is increased with CaO andFe₂O₃addition, but the coke strength after reaction is reduced. The rate of sulfur fixationis increased with the addition of additives. The inorganic sulfur in coke is mainly inform of CaS. The study of impacts of different additives on coke contents of water, ash,volatile, fixed carbon and sulfur indicates that the addition of additives could lead to thechange of the escape process of gaseous products evolved in coking and the addition of CaO and Fe₂O₃could accelerate the escape rate of water during the coal pyrolysisprocess.Next, the coal samples received in the coking of high sulfur coal with additiveswere using methods of XRD and SEM analysis. The crystallite structure parameters ofcoke were calculated and combined with SEM analysis, the effects of additives on cokecrystallite structure and surface morphology were investigated based a reference on thecoking products of original coal. The results indicate that:（1） Fe₂O₃and La₂O₃facilitatethe conversion of CaO to CaS. The crystallite structure parameter of coke, La, changesslightly. Additives La₂O₃increases the value of Lc while CaO and Fe₂O₃decrease it.Appending additional minerals mainly influence the portrait crystallite structureparameters.（2） CaO leads the pores of coke to increase with its physical action andagglomerating characteristic. Fe₂O₃and C can form （Fe,C） which leads to pore wallpulverization and erosion. La₂O₃makes the coke surface more compact and thinner.（3）Additives can change the crystallite structure and surface morphology of coke andhence change its reactivity.Finally, the ratio experiments with multi-additives （Al₂O₃、Fe、TiO₂、MnO、CaCl₂、B₂O₃、Fe₂O₃）were studied to reasonable compound additives. It was also studied toverify the feasibility of compound additives.