采用碱溶法分离回收燃煤电厂废SCR脱硝催化剂中的载体成分TiO2，通过正交实验考察了NaOH浓度、反应温度、固液比和转速对碱溶法回收TiO2过程中主要杂质W浸出分离、W和Ti浸出率的影响规律及浸出渣物相的变化规律，所得含钛浸出渣经20% H2SO4溶液或20% HCl溶液洗涤、煅烧回收TiO2。结果表明，反应温度对杂质W浸出影响最明显。回收Ti元素的最优条件为反应温度110℃及NaOH浓度40wt%、固液比1/5 g/mL、转速400 r/min，该条件下废SCR脱硝催化剂中W的脱除率达87.5%，Ti的溶出率仅为0.04%，浸出液中W/Ti浓度比为210。经H2SO4处理后生成锐钛型TiO2，经HCl处理生成金红石型TiO2，二者纯度均大于98%，实现了TiO2晶体的可控制备。
Recovery of TiO2 from spent selective catalytic reduction (SCR) denitration catalyst used in coal-fired power plants was studied by alkali hydrothermal method. The content of TiO2 as a carrier was 90%, which was the main component in spent SCR denitration catalyst. Due to the high content and suitable reaction Gibbs free energy change (ΔrG) value of WO3 in all oxide of spent SCR denitration catalyst except TiO2, it was selected as an example of impurity to remove. The effects of NaOH concentration, reaction temperature, solid to liquid ratio and stirring speed on the leaching of W element with low Ti leaching in the alkali hydrothermal process were determined by orthogonal experiment. Effect of each factor on the leaching rate of W and Ti and the change of crystal phase of the residua were further investigated. Finally, the optimal leaching conditions of separation W and recovery Ti were obtained. The results showed that the most significantly influence factors was the reaction temperature. Under the optimal leaching conditions of reaction temperature 110℃, NaOH concentration 40wt%, the ratio of solid to liquid 1/5 g/mL, stirring speed 400 r/min, the leaching rate of W reached 87.5% and Ti was 0.04%. Meanwhile, the leaching concentration ratio W/Ti was 210. Under the optimal process conditions, the crystal phase of leached residua completely changed from anatase TiO2 to amorphous titanate. The residua obtained under the optimal process conditions were washed by H2SO4 or HCl respectively in order to recover TiO2. The results showed that anatase TiO2 was generated by H2SO4 system, and rutile TiO2 was generated by HCl system. The purities of both TiO2 materials were higher than 98%. Recovery of TiO2 by alkali hydrothermal method showed a relatively low temperature (80?120℃) when the NaOH concentration was 20wt%?40wt%. It could realize the controllable recovery and utilization of titanium resources.
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