Recovery of vanadium and tungsten from waste selective catalytic reduction catalysts by K_(2)CO_(3) roasting and water leaching followed by CaCl_(2) precipitation

Waste selective catalytic reduction(SCR)catalysts are potential environmental hazards.In this study,the recovery of vanadium and tungsten from waste SCR catalysts by K_(2)CO_(3)roasting and water leaching was investigated.The roasting and leaching conditions were optimized:the leaching efficiencies of vanadium and tungsten were 91.19%and 85.36%,respectively,when 18 equivalents of K_(2)CO_(3)were added to perform the roasting at 900℃ for 2 h,followed by leaching at 90°C for 1 h.Notably,in the described conditions,the leaching rate of silicon was only 28.55%.Titanates,including K_(2)Ti_(6)O_(13)and KTi8017,were also produced.Si removal was achieved in 85%efficiency adjusting the pH to 9.5,and the Si impurity thus isolated was composed of amorphous Si.Tungsten and vanadium were precipitated using CaCl_(2).At pH 10 and following the addition of 0.10 mol of H_(2)O_(2)and 16 equivalents of CaCl_(2),the precipitating efficiencies of tungsten and vanadium were 96.89%and 99.65%,respectively.The overall yield of tungsten and vanadium was 82.71%and 90.87%,respectively.

K_(2)CO_(3)添加剂细水雾作用下高压氢气喷射火特性研究

为更好地抑制高压氢喷射火,研究了K_(2)CO_(3)添加剂细水雾作用下欠膨胀氢气喷射火特性。试验采用实心锥形细水雾喷嘴,考察细水雾在不同K_(2)CO_(3)添加剂质量分数、水平施加位置和施加压力下,对欠膨胀氢气喷射火火焰形态、火焰水平长度、羽流区温度及辐射的影响。试验采用摄像机、热电偶、辐射热流计分别测量火焰形态、空间指定点温度和辐射强度。结果表明,在含有K_(2)CO_(3)添加剂的细水雾作用下,氢气喷射火焰更明亮。细水雾压力较低(0.5 MPa)且施加位置位于火焰抬升位置时,氢气喷射火出现明显的火焰膨胀现象。通过与纯水细水雾进行对比发现,K_(2)CO_(3)添加剂细水雾对氢气喷射火稳定火焰长度、羽流区温度及热辐射的抑制效果明显,并且抑制效果随着K_(2)CO_(3)添加剂质量分数的增大而增大。