Removing Tin from Tin-bearing Iron Concentrates with Sulfidation Roasting Using High Sulfur Coal

Abstract

With the sulfidation roasting process using high sulfur coal, the tin could be removed efficiently from tin-bearing iron concentrates, and the iron phase was reduced to metal iron. The research showed that the tin removal rate increased with roasting temperature and residence time. Different with the phenomena using pyrite as curing agent, deep reduction of tin-bearing concentrates did not cause tin remove rate decrease. The reason may be that curing rate of tin phases by the SO 2 generated from high sulfur coal pyrolysis was higher, and the formation amounts of iron-tin alloy were decreased. The iron phase was mainly reduced into Fe from Fe 2 O 3 and Fe 3 O 4 in the roasting process. Tin content of the concentrates was decreased to 0.056% under the conditions of N 2 flow rate of 60 ml/min, roasting temperature of 1 473 K, residence time of 60 min, high sulfur coal addition amounts of 70% and particle size of 200 meshes. The roasting product can meet the standard of BF ironmaking, which requires tin content in iron ores less than 0.08%. The work supplies a new approach for the clean use of high sulfur coal.

Reduction and Sulfurization Behavior of Tin Phases in Tin-bearing Iron Concentrates with Sulfates in Sulfur-bearing Stone Coal

“…In the previous study, the tin could be effectively removed (Sn volatilization ratio > 90%) from tin-bearing iron concentrates by roasted with 70 wt.% sulfur-bearing stone coal under the conditions of N 2 atmosphere, roasting temperature of 1 200°C, residence time of 60 min and particle size minus 0.0750 mm. 10) The tin-bearing iron concentrate was firstly mixed with sulfur-bearing stone coal, grounded to minus 0.0750 mm, placed in a crucible, and then roasted in a tube furnace for a certain time under N 2 flow rate of 60 ml/min. It is difficult to determine the reactivity of sulfates in the sulfur-bearing stone coal for a low content.…”

“…4,[7][8][9] A method using sulfur-bearing stone coal to remove the excessive tin has been successfully performed on the laboratory level by the authors' group. 10) It is especially noteworthy that the Sn volatilization ratio has an obvious fluctuation with the variation of sulfur-bearing stone coal amount during the roasting process. In addition, previous studies have suggested that the sulfur occurs in inorganic and organic forms in sulfur-bearing stone coal.…”

“…13,14) It is necessary to determine the effect of sulfur in different forms on the reduction and sulfurization behavior of tin phases. The tin could be sulfurized and removed effectively by SO 2 in presence of organic sulfur 10) and by S 2 and FeS in presence of pyrite. 15) However, few researches paid attention to the reactivity of sulfates when roasted with tin-bearing iron concentrates.…”

Reduction behavior of Tin-containing phase in Tin-bearing iron concentrates under CO-CO2 mixed gases

“…Previous studies shows iron and tin in the tin-bearing iron concentrates exist mainly in forms of magnetite (Fe 3 O 4 ) and cassiterite (SnO 2 ), and the Sn phase is almost embedded in the iron phase (Fe 3 O 4 ) at finegrained size, resulting that recovery of tin is low by mineral processing methods [6]. The tin could be separated efficiently through the methods of reduction or sulfidation roasting processes [6][7][8][9][10][11][12][13][14][15][16]. Reductant is used in many metallurgical processes to control oxygen potential of the reaction system [17].…”

“…Using CO as the reductant, for the reduction roasting process, the Sn phase (SnO 2 ) is reduced and further removed in the form of gaseous SnO, through which the tin content in the iron concentrate can decrease to 0.08 wt.% with the original tin content being below 0.35 wt.% in the tin-bearing iron concentrates [11][12]. The sulfidation roasting process takes place at a higher rate at the point of Sn removal than the reduction roasting process when the Sn content in the tin-bearing iron concentrate is relatively high, in which the tin volatilization rate reaches over 90% using the FeS 2 or high sulfur coal [8][9]. In this process, the SnO 2 is reduced firstly and then sulfurized and removed by gaseous SnS.…”