From the 1960s on foreign iron ore anti-flotation process a lot of detailed work, they generally agreed that anti-flotation process has the following characteristics: â‘ in general can not desliming flotation; â‘¡ without high concentration of the pulp to flotation smoothly; â‘¢ the grade iron mineral stone changes little effect on the flotation process; â‘£ relatively easy to obtain a low impurity content of iron ore. Therefore, foreign countries (especially the Americas) have had a large number of industrial applications in the 1970s. The research on reverse flotation process in China began in the 1970s and was only put into industrial application in the early 1980s. However, it has only been widely applied since the beginning of this century.
1. Cationic collector floating silicon process
(1) Neutral medium flotation without inhibitor
The process is mainly used to treat the weak magnetic separation concentrate of magnetite ore to reduce the SiO 2 content in the magnetic separation iron concentrate. The addition of an amine-based cation collector , without the addition of an iron mineral inhibitor, is due to the poor floatability of magnetite in a neutral medium. Almost all of the foreign companies that implement magnetite anti-flotation and silicon reduction have adopted this process, such as the United States, Athens, Adams, Moose Mountain, and Griffith. Wait for the concentrator. The characteristics of these flotation processes are: fine materials (-0. 044 mm accounted for more than 90%), flotation and tailing, most of which have sweeping operations, and the iron grade of the floating materials is 63% to 66%. floating fine iron grade of 67% ~ 69% (SiO 2 content of 6% or less), the end of the floating iron grade from 23% to 35%, work-ferrous metals recovery of 93% to 96%.
So far, China's selection of plants using this process is still relatively small. The anti-flotation workshop of Anshan Iron and Steel Co., Ltd., which was put into operation in the early 1980s, used a reverse flotation-foam magnetic separation tail-magnetic re-grinding process. The iron concentrate grade increased from 61.5% to 65.5%. Discontinued; in 2001, the second process of Angang Steel Changling Mining Company adopted the same process, the grade of iron concentrate increased from 65.5% to over 68.5%, and the SiO 2 content fell below 4%. The difference between the anti-flotation process of China's related plants and the foreign countries is that the reverse flotation does not end, but the magnetic separation is used. The sweeping operation is not set in the process. The granularity of the materials to be floated is coarse, and the mine needs to be reground. Re-election, the grinding amount is larger, the grinding efficiency is lower, and the operation yield is generally 96% to 98%.
In addition, China has conducted research on the reverse flotation process of single oreamine collectors without inhibitors on raw ore or (weak, strong) magnetic separation concentrates of red iron ore, although small or semi-industrial tests have been successful. However, industrial trials failed to make breakthroughs due to the difficulty of handling flotation foam.
(2) Adding inhibitor alkaline media flotation
The process is a relatively versatile process, especially suitable for the ore sorting of high-grade red iron or magnesia or red-red mixed ore, and also suitable for the sorting of coarse ore (magnetic fine or fine) of the above ore. Due to the flotation in an alkaline medium (pH 10 ~ 10.5), and the addition of iron mineral inhibitors, the mud resistance of the flotation is enhanced and the foam properties are greatly improved, so the flotation process can be set coarse, fine, sweeping The operation can guarantee the high-quality iron concentrate, and at the same time, it can be tailed in the sweeping operation, and the process operation is easy to control. Generally, the closed-loop process structure in which the medium-mineral concentrate returns or partially returns to the rough selection and re-selection is adopted.
There are many red iron ore plants in the country. The typical concentrators include the Sept Iles plant in Canada and the Samarco plant in Brazil, both of which handle high grades. %-60%) of the original ore of red iron ore, the reverse flotation process is the same, the difference is that the former does not de-sludge directly for reverse flotation, while the latter is de-sludged by two-stage cyclone due to the large amount of primary slime. After the reverse flotation, the SiO 2 content of the iron concentrate was reduced to 5.5% and 2%, respectively, and the iron recovery rate was above 90%. In the last century, China's (weak, strong) magnetic separation concentrates such as Qi Dashan and Other iron ore in Anshan Iron and Steel Co., Ltd. also carried out large-scale industrial experiments on similar processes. For ore mines with an iron grade of about 29%, iron grades of more than 65% can be obtained. The total recovery rate is more than 78% of the technical indicators, but due to the constraints of the current source of amine collectors and pollution of water quality, the process has not been industrially applied. With the development of technology, Xinyu Iron and Steel Company Tiekeng Iron Mine implemented a cationic collector floating silicon process for limonite strong magnetic concentrate in 2005. Design indicators: 37% of original ore grade, 54.5% of concentrate iron grade, comprehensive The recovery rate is 50%.
It should be pointed out that the advantages of the cationic collector floating silicon process are: less variety of chemicals, lower cost, no need to carry out in high alkalinity medium, and little influence on filtration; disadvantages are: flotation foam is not easy to control It is sensitive to slime. The ammonia nitrogen in the amine collector is polluted by water quality, and the iron ore with more iron silicate mineral content is poorly sorted. Both domestic and foreign research and practice have proved that when iron-silicate silicate minerals (such as amphibole) are similar to the isoelectric point of useful iron minerals, when anionic collectors are used to float these iron silicate minerals, The result is a high foam grade and a large loss of useful iron minerals. This is a recognized technical problem in the industry at home and abroad, especially in recent years, how to solve this problem abroad has made a lot of research, and has made initial progress.
Second, the anion collector floating silicon process
The process is required to be carried out in a strong alkaline medium (pH=11.5 or so), an inhibitor of iron minerals (starch or lignosulfonate, etc.) and an activator of siliceous minerals (Ca++, etc.), which are captured by fatty acids. Collecting agent. Since the process is less sensitive to slime, it is possible to sort the iron ore without deliming. In the United States, Canada, the former Soviet Union and other countries from the 1960s on the low-grade iron oxide ore or semi-iron oxide ore for direct anion to the collector reverse flotation process test, the United States and Canada using starch as an inhibitor The former Soviet Union used lignin because of food shortages. Although the results of the United States and Canada have proved that the anti-flotation of anionic collector can also achieve the selection index of cationic collector reverse flotation, it is not due to the high cost of the former and the influence of concentrate filtration. Industrial application. The former Soviet Union study believes that the anion collector reverse flotation process directly treats low-grade iron ore, its cost of chemicals is high, lignin degradation is polluted by water quality, and iron concentrate is difficult to filter, so there has been no industry. Application report. According to reports, the former Soviet Union built an industrial test series in the Krivo Rouge Oxidation Mining and Production Company in accordance with the strong magnetic separation-anion reverse flotation process.
Since the 1970s, China has carried out research on the anion collector reverse flotation process for the poor red iron ore in Anshan. Due to the tight food supply at that time, the inhibitor used lignin sulfonate and in order to reduce the pharmacy. Cost, tends to reverse flotation of weakly magnetic and strong magnetic mixed coarse concentrates. During the "Seventh Five-Year Plan" period, China passed the technical research on the rational beneficiation process of Qidashan iron ore in Anshan Iron and Steel Co., Ltd., especially solved the problem of starch source. Finally, it was determined that the newly-built Tuanjuntai Concentrator used mixed-mine concentrate anion reverse flotation. Process, and built the first large-scale concentrator (9 million t/a ore) using anion reverse flotation process during the National Ninth Five-Year Plan. After several years of research, the iron concentrate grade of the Tuanjuntai Concentrator has reached more than 66%. The success of this process at the Tuanjuntai Concentrator has laid the foundation for the advancement of high-quality iron concentrate ore dressing technology in China. Subsequently, the Flotation Workshop of Qishanshan Concentrator of Anshan Iron and Steel Co., Ltd. was changed from acid positive flotation process to this process in 2001, and the original roasting-magnetic separation workshop was also transformed into the same process as the flotation plant in early 2002. Currently iron concentrate The grade has reached more than 67%. At the same time, the Maanshan Mine Research Institute has also achieved good test results for the use of this process in magnetite concentrates. For example, the iron concentrate of Taishan Jianshan Iron Mine can be increased from 65% to over 68.5%, and SiO 2 from 8 % is reduced to below 4%, and the operating yield is over 98%; the iron concentrate of Laigang Hanwang Iron Mine can be increased from 63% to more than 67%, and the SiO 2 content is reduced from 11% to less than 6%. The rate of 97%, the reverse flotation plant of the above two mines was completed and put into operation at the end of 2002. Subsequently, the anionic collector floating silicon process has been widely applied in concentrating plants such as Anshan-type lean iron ore, such as the Anshan Iron and Steel Mine in Anshan Iron and Steel and the Sijiaying Iron Mine in Tangshan Iron and Steel.
China is the first country in the world to promote the use of anion reverse flotation silicon removal process. It is suitable for the treatment of coarse concentrates. The commonly used processes are one rough selection, one selection, three sweeps, and medium mines. China's research and practice have proved that the use of Ca++ to selectively activate siliceous minerals and selectively inhibit iron minerals in strong alkaline media makes the difference in floatability between iron minerals and siliceous minerals larger. The flotation selectivity makes it possible to obtain both high-quality iron concentrates and low-grade tailings, and has good adaptability to changes in the properties of human floating materials, especially for iron-containing silicates. The sorting of materials with more minerals is obviously superior to the cationic collector floating silicon process. The shortcomings are that there are many varieties of chemicals, and the cost is slightly higher. Because the higher pH of the pulp has an effect on the filtration of the concentrate (can be solved by acid neutralization).
Third, selective flocculation degumming - reverse flotation silicon removal process
For the weak magnetic lean iron ore with very fine grain size, the other mud removal method will cause a large amount of iron metal loss. Therefore, the finely ground material is firstly subjected to selective flocculation to remove the mineral mud with lower grade, and then proceed. Reverse flotation removes silicon. The reverse flotation can use cationic collectors or anionic collectors. The key technology of the process is the selective dispersion and selective flocculation control of reasonable process parameters and stable desliming equipment. Selective flocculation and desliming is affected by many factors such as pH value, hardness, temperature, dispersant dosage, flocculant dosage, stirring strength, etc., so the operation control requirements are strict. A typical example is the Tilden concentrator in the United States. After extensive experimental research on various technical solutions, the final industrial application of selective flocculation desiccant-cation collector reverse flotation process. In China, the experimental research on related technologies such as Donganshan, Qidashan and Hunan Mindong of Anshan Iron and Steel Co., Ltd. has been carried out, and good test results have been obtained, but due to the complicated control of the whole process, etc. Has not been able to large-scale industrial applications.
Fourth, other reverse flotation impurity removal process
(1) Iron concentrate reverse flotation desulfurization
The harmful impurity sulfur in iron concentrate is generally in the form of pyrite and pyrrhotite. The sulfur in the form of pyrite can be removed by flotation or magnetic separation of xanthate, and pyrrhotite Sulfur in the form is difficult to remove because of its strong magnetic properties and its floatability is susceptible to various factors. Research and practice at home and abroad have proved that the surface of pyrrhotite is easy to oxidize (formation of iron hydroxide), muddy, magnetic agglomeration, etc., which greatly reduces its floatability. For this reason, in the flotation desulfurization, it is generally used. Acid scrubbing surface, dispersing agent dispersing, demagnetization, multi-stage activation, enhanced harvesting and other measures to improve the removal rate.
(Ii) reverse flotation of iron ore addition of phosphorus
Phosphorus impurities in iron concentrates mainly exist in the form of apatite and collophosphate, and a small amount is present as rare earth phosphate minerals. Although the floatability of phosphorus minerals is better than that of iron minerals, the difference in floatability between the two is not significant. Therefore, magnetic separation is generally used to remove the coarse-grained phosphorus minerals, and then reverse flotation In addition to phosphorus minerals in fine-grained inlays. In the reverse flotation, a large amount of water glass or an appropriate amount of starch is generally added to inhibit iron minerals, and an anionic collector is used to float phosphorus minerals. The suitable pH value is about 10, and the slurry heating is beneficial to improve the phosphorus removal effect. For example, the Grangesberg plant in Sweden and the Hipasam iron ore plant in Argentina have adopted this process in the industry. The phosphorus in iron concentrates can be from 1% and 0.45 respectively. % decreased to 0.016% and 0.16%; phosphorus (rare earth phosphorus) in iron concentrate of Baotou Steel Plant in China decreased from 0.3% to 0.15%; the results of phosphorus reduction test of iron concentrate in Meishan Concentrator showed that phosphorus can be obtained from 0.4% or so fell below 0.18%. Although this method is a current and simple process for industrial applications, generally the iron loss in the floating phosphorus foam is large, so the foam is usually recycled by magnetic separation and re-selection to reduce the iron loss.
In order to remove the phosphorus mineral together with the siliceous mineral, an anionic collector reverse flotation process using a strong alkaline medium (pH = 11 to 12), a starch as an inhibitor, and Ca++ as an activator may be employed. For example, Rana Grubery conducted a variety of phosphorus removal processes for iron ore in the Lana plant. It was concluded that the best results were achieved with this process, and the iron concentrate grade could be increased to 65. %, phosphorus content is reduced to less than 0.015%.
In addition, for the fine-grained phosphorus-containing weak magnetic iron ore, a selective flocculation de-sludge-anion collector (ca++ activation) reverse flotation process can be used to simultaneously remove impurities such as phosphorus and silicon, such as Tilden to the United States. The (Tilden) iron ore was tested by this process, and the results showed that the phosphorus removal effect of the process was better than that of the selective flocculation desiccant-cation collector reverse flotation process.
(3) Reverse flotation of iron concentrates to remove fluorine and alkali metal oxides (Na 2 O, K 2 O)
The fluorine in the iron concentrate is generally in the form of fluorite or rare earth fluoride. Usually in an alkaline medium, the iron mineral is inhibited by a large amount of water glass or an appropriate amount of starch, and the anion collector is used as an anti-mineral, such as Baotou Steel in China. The iron concentrate in the plant uses the anion collector reverse flotation process to remove fluorine, and the water glass as the dispersion and inhibitor. The fluorine content in the iron concentrate can be reduced from 1% to 2.4% to about 0.65%, but there is still iron. The problem of large loss and low fluorine removal rate. In addition, a process of adding starch as an inhibitor to a strong alkaline medium, adding Ca++ as an activator, and an atomic collector to float fluorine and silicon at the same time can also be used.
The alkali metal oxides in the iron concentrate are mainly present in the form of alkali metal silicate minerals (such as feldspar minerals, etc.). According to the physicochemical properties of the silicate minerals, the cationic flotation reverse flotation process is generally used. At the same time, it is proved that the addition of hydrofluoric acid is beneficial to increase the removal rate of alkali metal oxides, but it is necessary to extend the flotation time. To ensure the floating of silicon-containing minerals in iron concentrates.
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