Recovery of molybdenum is defined by recovery of molybdenum from containing molybdenum waste debris metallurgical process.
Molybdenum-containing waste materials are mainly the mixed waste molybdenum compounds, molybdenum powder, molybdenum sheet, molybdenum alloys, molybdenum-containing waste catalyst and so on. Recycled molybdenum in total production molybdenum accounts for a large proportion.
According to metal powder supplier, since molybdenum waste has a wide variety, recycled in different ways, often dominated by fire method, wet method is complementary. Common methods of regeneration molybdenum have sublimation method, zinc melting method, oxidizing roasting - acid leaching, sodium carbonate roasting - leaching and alkaline leaching. These methods only apply to recycle certain waste molybdenum - containing miscellaneous materials. Specific hybrid materials molybdenum - containing waste should be according to their specific ingredients and plant specific conditions select or develop applicable regenerative recovery methods.
Sublimation method is based on molybdenum metal at a certain temperature, can be oxidized into molybdenum trioxide and sublimation trap recycling methods (see molybdenum compound preparation), the recovery rate was up to 98%. Sublimation process was conducted in sublimation furnace, bag filter, exhaust fan and other components equipments, can be heated by electricity, gas, waste oil, coke and other heat source. Since molybdenum oxide is an exothermic reaction, once it reaches the intense sublimation temperature 923 ~ 1073K, molybdenum trioxide sublimation can be automatically proceeding. Sublimation obtained molybdenum trioxide by conventional return. This method suitable for the regeneration recycling of waste molybdenum powder, molybdenum ingot, molybdenum sheet, molybdenum wire, also applies to molybdenum rhenium alloys, high-speed steel grinding waste recycling.
Zinc melting method is suitable for the regeneration of cemented carbide and super alloy scrap recycling. Scrap cemented carbide and carbon and zinc mixed and heated to 1123 ~ 1273K, generating molten cobalt, nickel and zinc alloys. Release alloy and distilled zinc, and dissolved the distillation residue in mineral acid to recycle nickel and cobalt. The output of smelting zinc alloy by heating distillation zinc, and then calcined to volatilize molybdenum, with ammonia leaching tungsten in roasting residue. Cobalt, molybdenum, tungsten recoveries were 97%, 96.2%, 98.4%.
Oxidizing roasting - acid leaching method suitable for molybdenum-containing waste catalyst (typically containing MoO38% ~ 10%) recycled. Molybdenum-containing waste catalyst at 773 ~ 823K temperature calcine to remove carbon, hydrocarbons and sulfur, calcined product through pulverized in 473K temperature sulfuric acid solution leaching, filtered to make the potassium alum precipitate and cobalt-nickel-aluminum-vanadium-molybdenum leaching liquid separation. The filtrate add NaOH to make nickel and cobalt separated in hydroxide precipitated, after the liquid-solid separated, recover nickel, cobalt from the solid product. Molybdenum and vanadium in the form of Na2MoO4 and Na2VO3 remain in solution, then adding ammonium salt to make the vanadium in (NH4) 2VO3 precipitated, after separated, then by known conventional methods recovered vanadium and molybdenum. Cobalt and molybdenum recoveries were 97% and 95%.
Sodium carbonate roasting- leaching method is suitable for molybdenum-containing catalyst waste regeneration recycling. Molybdenum-containing spent catalyst adds sodium carbonate and coke, roasting in 1073K temperature, generate sodium molybdate, sodium vanadate, cobalt and nickel oxide. Due to spent catalyst contains 5% to 10% sulfur, and about 20% carbon, calcination by sulfur and carbon combustion can be self-heating. Calcination can be conducted in a rotary kiln or vertical furnace. Crushed the calcined product to a grain -0.075mm, then use 333K water leaching twice, sodium molybdate and sodium vanadate into solution, the leaching rate of molybdenum and vanadium is 97% to 98%, cobalt, nickel is few leaching and left in the leaching residue.
Alkali leaching method is suitable for molybdenum-containing nickel waste catalyst regeneration recycling. Molybdenum-containing nickel waste catalyst by crushing, alkali, high temperature melting, generates sodium molybdate and nickel oxide, sodium aluminate, and then pressurizing the flooding. In the leaching process, molybdenum and aluminum respectively in the form of sodium molybdate and sodium aluminate into the solution, while nickel in the form of nickel oxide left in the alkaline leaching residue. With sulfuric acid leaching nickel from alkaline leaching slag, after purification, preparing nickel sulfate. The leaching rates of molybdenum, aluminum, nickel were 96.9%, 86.7% and 90.1%.
Article Source:http://www.mhcmp.com
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