SCR Catalyst Recovery Process Improvement

SCR denitrification technology has the advantages of high denitrification efficiency, over 90%, good selectivity and reliable technology. Catalyst is the core of SCR denitrification technology. At present, the commonly used SCR denitrification catalyst is based on titanium dioxide as carrier, V₂O₅ as active component, WO₃ or MoO₃ as structural promoter. The activity of catalyst directly determines the efficiency of denitrification.

SCR catalyst belongs to hazardous solid waste, which will seriously pollute the environment. Meanwhile, various valuable metals contained in the failed catalyst have not been recycled, resulting in a huge waste of resources. Therefore, the recycling of failed catalysts can not only solve the corresponding risk of environmental pollution, but also turn waste into treasure and make full use of resources.

The following technical scheme can be used to separate vanadium and tungsten leaching liquor from the failed SCR denitrification catalyst: after mixing the failed SCR denitrification catalyst with sodium chloride at a mass ratio of 1:0.4-0.7, calcining at 850-900 ℃ for 2-4 hours, the mixture is mixed and separated with water at a liquid-solid ratio of 3-5:1 to obtain leaching liquor containing vanadium and tungsten, so as to realize the leaching of vanadium and tungsten. The specific operation is as follows:

(1)Raw material pretreatment: A power plant invalid SCR denitrification catalyst (main component V₂O₅-WO₃/titanium dioxide) was purged by clean and dry compressed air to remove the fly ash on the catalyst surface, in which the working pressure of compressed air was 0.5 MPa.

(2)Crushing: The invalid SCR denitrification catalyst in step (1) was crushed and uniform powder with particle size of 20-60 meshes was obtained.

(3)Sodium roasting: the catalyst in 10g step (2) was mixed with 5g sodium chloride powder uniformly, and roasted in muffle furnace at 900 ℃ for 2 h.

(4)Stirring: adding deionized water to the solid mixture roasted in step (3) with a liquid-solid ratio of 5:1, using a magnetic stirrer to stir the solid mixture to fully dissolve the water-soluble compounds, the magnetic stirring time is 3h, and the stirring temperature is 40 ℃, in order to achieve the leaching of vanadium and tungsten;

(5)Separation and extraction of vanadium and tungsten: 0.45um filter membrane was used to filter the mixtures after stirring, and the leaching solution of vanadium and tungsten was obtained. The leaching rate of vanadium and tungsten was 52.98% and 95.47% respectively.

Compared with the traditional process using sodium carbonate for roasting, the SCR catalyst recovery process uses sodium chloride for sodium roasting. The roasting temperature is also lower than that of sodium carbonate, which is more economical and environmentally friendly. In the roasting process, sodium chloride and vanadium in raw materials play a priority role. It not only saves energy, protects the environment, is safe and pollution-free, but also can obtain higher leaching rate of vanadium and tungsten at the same time.

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