According to reports, has proven reserves of molybdenite 30 percent of symbiotic with other minerals, mainly copper porphyry deposits are hosted by. Molybdenum production countries, except the United States, Canada and China have a single Lei molybdenum deposit, but more than about one-third of molybdenum is recovered as a byproduct from porphyry copper deposit in Peru, molybdenum, copper from Chile all beneficiation plant There are also a significant portion of molybdenum from the copper concentrator in the United States and Canada. The ore dressing development of porphyry copper deposits in China is relatively late. Now it is mainly Dexing Copper Mine. In addition, there are Xiaosigou, Baoshan, Tongshankou and Bai Naimiao copper mines. The study of the process of recovering molybdenum from porphyry copper ore is beneficial to accelerate the development of China's molybdenum beneficiation technology . This paper mainly discusses the technical problems of flotation of copper concentrate containing molybdenum from porphyry copper ore and separation of copper and molybdenum and molybdenum concentrate. The porphyry copper deposits are generally large-scale low-grade deposits containing 0.5-0.8% of copper, 0.01-0.03% of molybdenum, and tens of times to nearly a hundred times of copper. For this ore, the beneficiation process is selected by copper-molybdenum mixed coarse selection, and the coarse concentrate is re-grinded to select the molybdenum-containing selection. First, copper and molybdenum separation At present, there are two processes for separating copper and molybdenum. The molybdenum-free float copper process is complicated in operation, high in cost, and the molybdenum recovery rate is not too high. The only Bingham copper mine in the United States that currently uses this process is the copper flotation, copper tailings re-election plant and molybdenum recovery plant. The molybdenum recovery plant has two molybdenum concentrates. One is a copper sulphate concentrate from a copper flotation plant, which uses ethyl xanthate float copper, and a dextrin-and-molybdenum process for molybdenum-copper separation. The other is that at the same time as the above-mentioned molybdenum concentrate is produced, the copper concentrate foam is selected, and the selected tailings are combined with the concentrate from the copper tailings re-election plant. After thickening, filtration and filter cake roasting treatment , re-slurry, fuel oil floating molybdenum, Garnox copper, iron , plus sodium silicate stone, flotation foam selected three times to obtain a second molybdenum concentrate product, and the bottom of the tank is the second A copper concentrate. U.S. recently closed bell silver (Silver Bell) copper molybdenum processing plant also uses a floating suppressing copper process. The molybdenum inhibitors used in the molybdenum-spray copper process mainly include dextrin, starch, gum arabic and other organic gums. Not long ago, US Patent No. 2187930 introduced a condensation product of alcohol and aromatic sulfuric acid as an inhibitor of molybdenite. The copper-free molybdenum-molybdenum process is widely used. The crystal structure of molybdenum ore is arranged in layers by S-Mo-S, and the layer is layered with S-S bond. It is hydrophobic and has natural floatability. Sex. Only in the case of over-grinding, some of the fractures occur in the S-Mo bond and have a certain degree of polarity (hydrophilicity), and due to the mineral symbiosis, the floatability of the molybdenite is disturbed, and at the same time, the separation of copper and molybdenum In the previous stage of copper-molybdenum mixed flotation, the various chemicals used also affect the floatability of molybdenum ore. In addition, different copper minerals also require separate agents to be targeted. Therefore, the molybdenum-activated molybdenum molybdenum is much more complicated than a single molybdenum ore. In actual production, before the separation of copper and molybdenum, the following measures are often used to increase the difference in floatability of copper and molybdenum: 1 Concentrate and remove the copper-molybdenum mixed concentrate to reduce the influence of the mixed-selection agent on the separation, and some even filter The filter cake is re-pulped and separated. 2 heat treatment, including slurry steam heating and cake baking at low temperature. The purpose is to destroy the collector adsorbed on the copper surface, and cause a certain degree of oxidation of copper surface, so that the copper floatability is reduced. 3 An oxidizing agent such as hydrogen peroxide is added to oxidize and detach the collector adsorbed on the copper surface. Which measure is to be determined based on different copper minerals is also measured by economic benefits. 1. Copper minerals are chalcopyrite, and sulfides are usually used as copper inhibitors. Sodium hydrosulfide and sodium cyanide are generally used as copper inhibitors in foreign countries, sodium hydrosulfide is used in the separation of copper and molybdenum and molybdenum selection, and sodium cyanide is used in the later stage of molybdenum selection. Sodium sulfide is used in the Soviet Union and China. It is sometimes advantageous to add ammonium sulphide pretreatment before adding the sulphide. Satisfactory results can also be obtained using Phospho- Knox (commonly referred to as Knox) ​​or sodium ferrocyanide, such as the Ray, Mineral Park copper beneficiation plant in the United States. The use of sulfide as a copper inhibitor requires the slurry to be alkaline and added in batches to avoid wastage of sulfide oxidation. The amount of sodium sulfide is usually between 8 and 30 kg/ton of mixed concentrate. It is generally believed that steaming is the most effective separation method prior to the addition of the inhibitor. An example of a copper beneficiation plant using sulfide as an inhibitor is shown in Table 1. Table 1 Examples of copper selection plants using sulfide inhibition method 2. The copper mineral is a chalcopyrite. Arsenic Knox and sodium ferrocyanide are generally used as inhibitors. Some add an oxidant such as hydrogen peroxide, sodium hypochlorite, potassium permanganate pretreatment. In the later stage of molybdenum selection, sodium cyanide is often added. When using sodium ferrocyanide, the pH of the slurry should be between 7.5 and 8.5 and should not exceed 8.5. Chile's Chuguicomata is a typical example. The quarry reserves of Chuquicamata are 10 billion tons, and the processing capacity of the plant is 7,200 tons/day, which is one of the world's largest mines. The ore is mainly composed of chalcopyrite and pyrite. It contains up to 2.1% copper, 0.05% molybdenum and 1.8% iron. It is a rare porphyry ore with high copper and high molybdenum. The molybdenum selection process of the plant is: the molybdenum-containing copper concentrate from the thick pool grit, after two sets of scrubbing machines, the high concentration is strongly stirred, scrubbing off the chemical film on the surface of the copper concentrate, reducing the copper floatation, and then adjusting Rough selection of pulp. The chalcopyrite inhibitor Anamol D (arsenic Knox) ​​and sodium cyanide were added during the rough selection. The bottom of the rough selection tank is copper concentrate. The rough-selected foam is selected once, and the obtained foam is subjected to three times of selection after being strongly dehydrated. After the fourth selected foam enters the regrind machine, it is selected for the fifth time to obtain qualified molybdenum concentrate. The separation of copper and molybdenum using Anamol D is based on the ore nature of arsenic trioxide (As 2 O 3 ) and sodium sulfide (Na 2 S) I. When used, the acid is made into a 20% aqueous solution. 75% of Anamol D is added to the rough selection, 10% is added to a selection, and 5% is added to the second, third and fifth selections, and the total amount is 1.1 kg/ton of molybdenum concentrate. Sodium cyanide was added to the three selected and five selected, total amount of 1.1 kg / ton of molybdenum concentrate. The obtained copper concentrate grade is 40-42%, the recovery rate is 90-92%; the molybdenum concentrate grade is 53-55%. The recovery rate is 65%. The annual output of molybdenum concentrate is 1.2-15,000 tons, which is equivalent to the output of a large molybdenum plant. El Salvador in Chile and Toguepala in Peru are also the methods of beneficiation of typical chalcopyrites. 3. Mixed copper minerals. Such as porphyrite, the use of chalcopyrite-based inhibitors such as sulfides and Knox. Pin Tovalley and Bagdad in the United States; Gaspe and Lornex in Canada fall into this category. The selection and inhibition method of the inhibitor is affected by the agent used in the copper-molybdenum separation flotation process. Usually in the copper-molybdenum mixed flotation, the agent is mainly selected from the copper selection angle, and most of the yellow medicine and the yellow ester Z-200 are used. The black medicine is not used alone, and the black medicine is always mixed with other collectors. Chalcopyrite-based copper minerals, mixed flotation using xanthate, in the separation of copper and molybdenum, the use of sodium ferrocyanide alone is not ideal; using steam heating to destroy the adsorbed xanthate on chalcopyrite The effect is not obvious. A preferred method is to use ferrocyanide after pretreatment with hydrogen peroxide at a certain pH. For copper minerals dominated by chalcopyrite, yellowing is used for mixed floatation. In the separation of copper and molybdenum, it is effective to use ferrocyanide after pretreatment and other inhibitors; The yellow drug adsorbed on the surface of the copper ore is also feasible; the yellow drug adsorbed on the surface of the oxidized oxidized copper ore is also a method of attention. When a black drug mixed collector is used, when a copper-molybdenum is separated, a general oxidizing agent is used, and it is difficult to destroy the black drug adsorbed on the surface of the copper mineral by hydrogen peroxide; a steam heating method can achieve a certain purpose. Only the use of sulfuric acid as a strong oxygen agent works. The so-called "Morlensi" copper-molybdenum separation method is aimed at the use of black medicine and petroleum mixture foaming agent in the mixed flotation, while the copper and molybdenum separation with lime cooking has little effect on removing the black surface of the copper surface; It is economically unreasonable; it adopts dextrin to suppress molybdenum floating copper, and because of the crude selection of petroleum mixture, the suppression effect is not good, and the method of removing black medicine by strong oxidizing agent sulfuric acid is adopted. The copper-molybdenum separation process of the Molunxi copper mine firstly adds sulfuric acid and sodium ferrocyanide to the agitation tank from the thick pool of copper concentrate, and the copper bottom concentrate is coarsely selected at the bottom of the tank. The medicine, the grit is re-added with sulfuric acid and sodium ferrocyanide, and then selected, and the selected foam is added with sulfuric acid, sodium ferrocyanide and polysulfide for stirring and flotation. Two selected foams plus ferritic cyanide stirring, flotation, three selected foams are thickened, filtered, re-ground, and finally selected 6 times to obtain qualified molybdenum concentrate, the last selection to use high Concentration of sodium cyanide solution. This method requires strict operating conditions. Japanese Patent No. Sho 45-35162 proposes a method of separating copper-molybdenum after treatment with black powder mixed copper-molybdenum flotation concentrates: First, the mixed copper-molybdenum concentrate is concentrated to 40-60% solids of foam, and then adding fuel soluble metal sulfate Salt (such as copper sulfate, zinc sulfate), add acid to make the pulp pH between 5.5-7.5, add oxidant (such as hydrogen peroxide, sodium hydrogen hydride), and finally add copper inhibitor (such as sodium ferrocyanide, Knox or sodium sulfide, etc., can achieve better results in copper and molybdenum separation. 2. Nitrogen is used as a pneumatic medium for separation of copper and molybdenum Separation and recovery of molybdenum concentrate from copper-molybdenum mixed concentrate, the cost of copper inhibitors accounts for almost 70-90% of the cost of molybdenum concentrate. Therefore, reducing this part of the consumption of chemicals is a key technical and economic problem for the separation of copper and molybdenum. Save decanted inhibitor is consumed, it was heated pulp, causes the pulp to reduce the oxygen content, the occurrence of mildly oxidized copper surface; increased amount of lime, King pH value put out protect SH - effect; plus inhibitor before adding before use Ammonium sulfide is stirred; even the copper-molybdenum mixed concentrate is stacked in the atmosphere for a certain period of time, allowing the air to slowly oxidize the copper surface. These methods have certain effects and are also used in some factories and mines. It was not until 1972 that some experiments proved that the use of nitrogen or other inert gas as a gas-filling medium in the separation of copper and molybdenum can reduce the amount of copper inhibitor to 1/5-1/2, thus obtaining a patent. Since the introduction of this technology in the 1980s, it has achieved gratifying results. In 1981, Peru's Cuajone was the first to successfully use nitrogen in production, reducing the amount of inhibitor Anamol D by 50-70%. The Gibraltar (Gibraltor) copper mine has done a lot of work on nitrogen testing and industrial applications. Experiments have shown that the use of nitrogen, sodium hydrosulfide is reduced from 9250 g / ton to 2200 g / ton when using air, which saves 76.2% of sodium hydrosulfide. The separation process and process conditions of the plant are shown in Figure 1. The mine also carried out three technical and economic comparisons of 560 m3 /h nitrogen generators (refrigerated, combusted and pressurized cyclone adsorption) to find the most economical nitrogen generator. Figure 1 Gibraltar copper and molybdenum separation process The nitrogen test results of the US Shuangfeng Concentrator are shown in Figure 2. It is apparent from the figure that when air is used as the aeration medium, at the moment of flotation, the sudden loss of the effect of the inhibitor occurs, and with nitrogen, the suppression effect is almost constant throughout the flotation process. At present, foreign copper companies such as Pima, Cyprus, Anaimax, Lonex, Gaspe and Haimant use nitrogen gas, which generally saves 50-75% of copper inhibitors. With the increasing use of nitrogen in the separation of copper and molybdenum, technical problems such as flotation equipment and nitrogen recovery have been further improved. Wimco Equipment has designed and produced a 1.7 m 3 closed Wimco flotation machine, including nitrogen preparation and nitrogen recycling, as well as nitrogen and flotation columns. example. Third, the removal of impurities in molybdenum concentrate According to China's molybdenum concentrate standard or the international market requirements for molybdenum concentrate quality, in addition to the molybdenum content to reach a certain index, other impurities must also be lower than a certain index, otherwise it will reduce the price and cause economic losses. Common impurities in molybdenum concentrates are copper, iron, aluminum , tin , tungsten, silicon, calcium, and the like. In the molybdenum ore beneficiation process, the suppression of impurities has been considered from the process flow to the pharmaceutical system. However, due to the complexity of the ore properties, specific chemical treatments should be applied to the impurities during the beneficiation process to ensure that the impurities in the molybdenum concentrate are below the standard. Hundreds of simple introductions to the removal of various impurities. (a) silica Most molybdenum deposits are present in quartz veins, especially porphyry and skarn, and their composition is mainly silica. In the beneficiation process, water glass is generally used to suppress silica. Due to the close symbiosis of some silicas with molybdenite, the strong inhibition of silica will result in the loss of symbiotic molybdenite. Therefore, only by re-grinding to a certain fineness, the molybdenum ore monomer can be dissociated to reduce the silica content; on the other hand, since the molybdenite is not excessively ground, it is necessary to dissociate the molybdenum monomer by re-grinding. It is gradual, that is, it is necessary to adopt a multi-stage grinding method. The test of the Jinduicheng molybdenum mine fully satisfies this relationship. Table 2 shows the results of sieve analysis of molybdenum concentrate. It can be seen from the table that as long as it is ground to 0.034 mm, the molybdenite grade can reach more than 51%, and the silica content drops below 6%. Figure 3 shows the relationship between the number of regrind segments and the grade of molybdenum concentrate. Obviously, when the number of regrind segments is large, the number of selections is reduced, and the molybdenum grade is significantly improved, and the silica content of the phase is also reduced. Table 2 Screening results of molybdenum concentrate (%) In addition to the silica-removing glass, sodium fluorosilicate, sodium hexametaphosphate, sodium pyrophosphate, or the like may be used, or may be used in combination with CMC. (2) Layered silicates (such as talc, etc.) The floatability of this type of mineral is very good, and it is very similar to the floatability of molybdenite. Therefore, the separation of the two is quite difficult, and the quality of molybdenite is often unqualified. For this reason, the talc-containing plant, such as the Pima plant in the United States, uses a talc-containing molybdenum ore to be treated with a weak base strong acid salt such as ammonium sulfate solution, and then treated with a strong base weak acid salt such as sodium silicate solution. Molybdenum ore flotation. The Shuangfeng Concentrator uses sulfonated lignin to inhibit molybdenum ore for reverse flotation with satisfactory results. Due to the large amount of talc, the mine contains only 20-40% molybdenum in molybdenum concentrate. The sulfonated lignin and lime float were used to control the molybdenum talc with a pH of 11.5. The talc was removed by a coarse and fine slag. The bottom of the tank was a molybdenum concentrate with a molybdenum content of 47% and a recovery of 85-92%. The amount of sulfonated lignin depends on the amount of molybdenum, generally 8-12 kg / ton concentrate. It is also used in the process of adding molybdenum sulphate or ammonium sulphate in the process of molybdenum sulphide. The final operation and the addition of water glass can also achieve the purpose. (three) carbon The carbon in the molybdenum concentrate is mainly derived from the ore itself, and also from the impureness of the sodium sulfide used in the separation of copper and molybdenum. It has been found that there are three types of carbon present in molybdenum concentrates, namely bitumen , graphite and coal . The floatability of carbon is very good, generally with the foam entering the molybdenum concentrate, causing the grade of molybdenum concentrate to drop or fail. For bitumen-like carbons, such as the Kebel Concentrator, the mine contains a large amount of hard bitumen; they use a strong scrub in the special tank to remove the unqualified molybdenum concentrate, and then treat a selected concentrate through a cyclone, The asphalt-containing overflow is classified into the molybdenum rough-selected tailings. At present, the Bartlex chute and the Wiltley shaker have been used to remove the asphalt. The Ailan copper mine also contains bitumen. They have tested six carbon removal methods. The most economical method is to use a hydrocyclone with a diameter of 2.54 cm and a cone angle of 60 degrees (commonly known as a small diameter large cone angle swirl). The two-stage cyclone combination can control the grade and recovery according to different combinations. The results of the six carbon removal methods are shown in Figure 4, and the combination of the two-stage cyclones is shown in Figure 5. Figure 4 Decarburization rate and molybdenum recovery rate of six kinds of processing Figure 5 Two-stage cyclone loop combination For graphite carbon, such as the Tongshankou copper mine in China, graphite carbon is present in the silicate gangue. In the molybdenum concentrate obtained by flotation, the ratio of molybdenum to carbon is almost 1:1. The mine adopts the method of separate treatment of the middle ore, that is, the concentrated dewatering of the medium ore to exclude some fine-grained carbonaceous materials; and the sedimentation with ferric chloride, water glass and sodium hexametaphosphate inhibits the carbonaceous silicate. Therefore, a molybdenum concentrate having a grade of more than 45% and a carbon content of 3% or less can be obtained, and the recovery rate of molybdenum operation is about 70%. For coal-like carbon, such as China's Yihua molybdenum ore, the test shows that the combination of sodium hexametaphosphate and CMC can reduce the grade of molybdenum concentrate to 45.22%, carbon to 5-6%, and molybdenum recovery rate to 85.12%. Dexing's molybdenum concentrate contains carbon. The experimental shaker can remove 82% of carbon, which increases the molybdenum grade by 32% to 45% and the molybdenum operation recovery rate by 90%. In addition, the carbon-containing molybdenum concentrate is firstly stirred with a hydrocarbon (such as oil), and then stirred with hot sodium sulfide, and then floated to separate the carbonaceous material; there is also a claim to use a heavy medium separation method; The carbon-containing molybdenum concentrate is calcined (about 260 ° C) and the organic carbon is burned off. In short, there are many ways to remove carbon, but first of all, to identify the type of carbon, and then take the appropriate treatment. However, the effect of removing carbon has not been satisfactory so far, and it is not that the recovery rate of molybdenum is low, that is, the cost is too high. (four) sulfur Generally, ammonium sulfide is continuously stirred in the molybdenum selection to dissolve the sulfur. (5) Mica The common method is to strictly control the amount of water glass in the molybdenum roughing to reduce the floatability of mica; the other method is to remove the mica of less than 20 microns by the fractional deliming method in the molybdenum selection. (6) Fluorite Fluorite can generally be inhibited by potassium hydride (sodium). (Vii) galena Common weight Chromium Potassium (sodium) or phosphorus pentasulfide (Knox) inhibition of galena. (8) Copper, iron, arsenic and other sulfide minerals It is usually used with sodium sulfide or sodium hydrosulfide, cyanide, and a mixture of the two to obtain a satisfactory inhibitory effect. Fourth, chemical dressing The addition of different inhibitors to the molybdenum selection mentioned above can inhibit impurities in the molybdenum concentrate. However, with the competition of market trade, higher requirements are placed on the quality of molybdenite. In addition to the requirement that the molybdenum content in molybdenum concentrate should be as high as 53% or more, the content of other impurities is lower than the national standard. For this reason, the molybdenum concentrate obtained by the flotation method tends to further reduce the impurity content by chemical beneficiation. Usually, the impurities exceed copper, iron, lead and calcium. Several commonly used chemical beneficiation methods are as follows. The flotation molybdenum concentrate of Jinduicheng molybdenum mine contains more than 53% molybdenum, but lead and calcium are still exceeding the standard. To this end, the molybdenum concentrate was adjusted to a 50% (solid) slurry, and a leachate (2% hydrochloric acid, 6% ferric chloride) was added, and the solid-liquid ratio was 1:3, and the pH was 1.0. The leaching temperature was controlled at 50-80 ° C and leached for 1 hour. Part of the filtrate is then filtered back to the formulated leachate and the excess is discarded. The filter cake was rinsed three times with water and the rinse was discarded. The filter cake is dried to obtain qualified molybdenum concentrate, the lead content is reduced from 0.174% to 0.032%, and the calcium oxide is reduced from 0.54% to 0.048%. See Table 3 for comparison of indicators before and after leaching. Table 3 Quality comparison before and after chemical beneficiation of molybdenum concentrate (%) The Henderson molybdenum mine in the United States was leached with 5% hydrochloric acid at 80 ° C for 28 hours, and the lead content was reduced from 0.2% to 0.03%. The Brenda copper mine in Canada uses the method proposed by the No-anda Research Center, using a leachate consisting of 1% copper chloride, 10% ferric chloride, 30% calcium chloride and 0.5% hydrochloric acid. The leaching temperature was 100 ° C and leached under normal pressure for 2 hours. Results The leaching rates of copper and lead all reached 98%, the copper content decreased to 0.068%, the lead content decreased to 0.05%, and the calcium leaching rate was 79%.
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