Characterization and recycling of nickel- and chromium-contained pickling sludge generated in production of stainless steel
来源期刊：中南大学学报(英文版)2014年第8期
论文作者：LI Xiao-ming(李小明) XIE Geng(谢庚) HOJAMBERDIEV Mirabbos CUI Ya-ru(崔雅茹) ZHAO Jun-xue(赵俊学)
文章页码：3241 - 3246
Key words：stainless steel; pickling sludge; characterization; recycling; sulfur; fluorine
Abstract: Pickling sludge generated during the neutralization of pickling wastewater with calcium hydroxide in stainless steel pickling process was characterized using X-ray fluorescence spectrometry, X-ray diffractometry, scanning electron microscopy, thermogravimetry and differential scanning calorimetry, etc. The major compositions of pickling sludge are CaF2, CaSO4, Me(OH)n (M: Fe, Cr, Ni), and the content of CaF2 is high in the sludge. The melting point of pickling sludge is about 1350 °C and the viscosity is about 0.14 Pa·s at 1450 °C, which are comparatively lower than those of normal refining slag. After heat treatment, the contents of sulfur and fluorine in the pickling sludge were reduced, confirming the thermal decomposition of sulfate in the sludge. Fluorine in the sludge is reduced by the gaseous SiF4 and AlF3 generated through the reactions of CaF2 with SiO2 and Al2O3. The preliminary results from the reduction test indicate that the sulfur content in the steel is not affected by the presence of sulfur in the sludge. The recovery of nickel is about 40%, and the chromium content changes marginally due to the protective atmosphere under the reduction condition of chromic oxide. The pickling sludge is a potential auxiliary material for the production of stainless steel.
LI Xiao-ming(李小明)1, XIE Geng(谢庚)1, HOJAMBERDIEV Mirabbos2, CUI Ya-ru(崔雅茹)1, ZHAO Jun-xue(赵俊学)1
(1. School of Metallurgical Engineering, Xi’an University of Architecture and Technology, Xi’an 710055, China;
2. School of Materials Science and Engineering, Xi’an University of Architecture and Technology,
Xi’an 710055, China)
Abstract:Pickling sludge generated during the neutralization of pickling wastewater with calcium hydroxide in stainless steel pickling process was characterized using X-ray fluorescence spectrometry, X-ray diffractometry, scanning electron microscopy, thermogravimetry and differential scanning calorimetry, etc. The major compositions of pickling sludge are CaF2, CaSO4, Me(OH)n (M: Fe, Cr, Ni), and the content of CaF2 is high in the sludge. The melting point of pickling sludge is about 1350 °C and the viscosity is about 0.14 Pa·s at 1450 °C, which are comparatively lower than those of normal refining slag. After heat treatment, the contents of sulfur and fluorine in the pickling sludge were reduced, confirming the thermal decomposition of sulfate in the sludge. Fluorine in the sludge is reduced by the gaseous SiF4 and AlF3 generated through the reactions of CaF2 with SiO2 and Al2O3. The preliminary results from the reduction test indicate that the sulfur content in the steel is not affected by the presence of sulfur in the sludge. The recovery of nickel is about 40%, and the chromium content changes marginally due to the protective atmosphere under the reduction condition of chromic oxide. The pickling sludge is a potential auxiliary material for the production of stainless steel.
Key words:stainless steel; pickling sludge; characterization; recycling; sulfur; fluorine
