62results about How to "Direct discharge" patented technology

The invention relates to the field of flue gas denitration, and specifically relates to a method capable of completely recycling tungsten trioxide from an SCR catalyst. The method comprises the following steps: soaking grinded waste catalyst in water with a volume three to four times as large as that of the waste catalyst to remove the impurities; adding an excess alkali solution with a concentration of 60 to 80wt% into the purified powder, soaking for 3 to 5 hours at a temperature of 140 to 150 DEG C, filtering, condensing the filtrate to recycle the alkali, adding acid into the condensed liquid from which the alkali has been crystallized to adjust the pH value to a range of 7 to 8, filtering to remove the generated silicic acid so as to remove the silicon element, adjusting the pH value of filtrate to 10 or more, boiling the filtrate to carry out tungstate radicle uniformity, cooling the filtrate temperature to 60 to 80 DEG C, dropwise adding the filtrate into 8-12 mol / L nitric acid with a volume as large as that of the filtrate, cooling, and filtering so as to obtain high purity yellow tungstic acid. The method can carry out complete sodium modification on tungsten trioxide without burning, thus low level of tungsten trioxide can be completely converted into tungstic acid, moreover, and the silicon element is completely removed, so the one-time cost of factory building and operation consumption are both largely reduced.