The method of purification of iron ore concentrate from the impurities of phosphorus

 

(57) Abstract:

The invention relates to the preparation of iron ore concentrates for metallurgical treatment by improving their quality due to the removal of undesirable impurities contained in concentrates, primarily phosphorus. The method of purification of iron ore concentrates from phosphorus includes roasting, cooling, leaching with a mineral acid under given parameters of leaching, separation of the liquid phase from the solid, and iron ore concentrate is subjected to oxidizing roasting at a temperature of 800-1000oWith aged no more than one hour. The leaching is carried out with sulfuric or nitric acid, with the specific choice of the acid is carried out depending on the mineralogical composition of the ore and the structure of matter, which is the carrier of phosphorus, provided the production of standard phosphorus iron concentrates. 4 C.p. f-crystals, 1 table.

The invention relates to the preparation of iron ore concentrates for metallurgical treatment by improving their quality due to the removal of undesirable impurities contained in concentrates, primarily phosphorus.

For industrial applications of iron ore concentrates to which the impurities. For blast-furnace production requires that the content of phosphorus in iron ore concentrate does not exceed 0,25-0,30%.

Depending on the composition of iron ores are being developed technologies for enrichment and further training for metallurgical treatment.

Despite the fact that the number of low quality ores is relatively small, approximately 10-20% of the world reserves, bringing them up to standard with the aim of further involvement in the economic turnover and sales is relevant and very complex problem.

When the ore is often faced with difficulties in the production of standard phosphorus concentrates. For tungsten ores, for example, this problem is successfully solved by the use of chemical refining of concentrates. In recent years much attention is paid to this issue during the concentration of manganese ores. Begins to apply chemical enrichment of iron ore for the selective removal of silicates.

The problem of development of technology for removal of phosphorus not by metallurgical and obtain from these ores conforming phosphorus concentrate is of great practical interest and is important not only for CIS countries, but also of the Sabbath., in such ores, the iron content is 30-49% (minimum for concentrates - 50%), and the phosphorus content of 0.6-0.9% and more.

Ore, often layered nature of the oolitic structure, often deformed, consists mainly of gidrogenit, chlorite and calcium phosphate. The oolites fractured, so weakly resist crushing.

Magnetite presents fine crystalline particles smaller 0,050 mm Ore can be weakly oxidized (partitition). Chlorite type samoasite; it contains magnesium and ferrous iron.

Calcium phosphate belongs to a group of Apatite; its molecule may contain one or more groups, IT and possibly a bit SiO2instead RHO4. Its morphology can vary amorphous and pseudodictionary.

A well-known theory that the phosphate anions absorb and grow on the surface of ferrihydrite gel and the phosphorus is removed from the lattice of iron ore inside the crystals dehydrate liquid cement and recrystallized. Limited phosphorus removal is achieved by grinding and magnetic separation, partly technically possible, so this technology is the removal of phosphorus from iron ore as a result, Therefore, the mechanical methods cannot remove it until the contents, satisfying the requirements of metallurgical production.

Due to the impossibility to significantly reduce the phosphorus content in concentrates by means of mechanical processing known application of hydrometallurgical methods for obesfosforivanie iron ore.

For example, French patent 1505100, 1963, the Essence of it is that crushed to a particle size of 0.5 to 0.05 mm ore treated poorly concentrated (from 0.5 to 2%) sulphuric acid solutions with a large dilution with stirring for 10 to 25 hours. The regeneration solution made by ion exchange with resins based on polystyrene.

The disadvantages of this method include the length of the process, the need for regeneration of significant quantities of solution.

The known method of preliminary treatment of the ore to reduce the content of sulfur and phosphorus by washing ore (essentially iron oxide) aqueous solutions of soda with a gradual temperature increase (U.S. patent 3928024, With 22 In 1/11, publ. 23.12.1975 year).

The known method includes mixing an inorganic substrate with the oxide ore containing mainly iron oxides in the ratio of about 0.1: 1.5 fundamentals to the addition method include, the degree of reduction of the impurities of phosphorus in the ore is low and, therefore, not possible to get conditioned iron ore concentrates.

In recent years the most common ways of dephosphorization metal-containing ores are chemical methods - alkaline or acid leaching with the Department Vasilchenko concentrate.

A known method of removing phosphorus from Lorraine iron ore containing 30% Fe, 20% SIO, SIS2, 7% Al2O3and 1.7% P2O5where used processing ore 40-50% alkali solution at a temperature of 125-140oWith duration from 30 minutes to 3 hours and the amount of solid in the slurry is from 50 to 200 g/l was extracted into a solution to 60-80% of phosphorus, silica and other minerals ore, iron recovery in concentrate more 93-95% (VIII international Congress on mineral processing, so 2, Leningrad, 1969, "Mekhanobr").

As the alkali, the most widespread sodium hydroxide, with get-low-tech solutions, which are poorly defended and filtered.

In addition, we identified the optimal mode leaching had a number of serious disadvantages: complex scheme of regeneration eloallitasa ores, involved in the handling of the material by the method of oxidative leaching in an acid medium under such conditions, in order to promote the oxidation of iron and sulfur to oxidize sulfide sulfur, at least partially in sulfate and oxidized iron and impurities go into solution in the leaching process, which is conducted over a period of time, while more than 80% of the sulfide contained in the material, not to oxidize. This forms a precipitate leaching, which is suitable for chernometallurgicheskih reduction of iron (U.S. patent 5397380, he PCT WO 09222573 from 23.12.92, With 22 In 1/11, 22, 3/04, publ. March 14, 1995).

This method gives a positive result for sulfur removal, but does not provide dephosphorization iron ore.

There is a method by which samples of ore after grinding to a particle size 0,043 mm were subjected to beneficiation magnetic separation in a weak field. Were obtained concentrates with content about 62-63% Fe, 4% SiO2, 3% Al2ABOUT3and 0.4% P; output averaged about 63% of the original ore; the extraction of iron in the concentrate is 75%, and the extraction of magnetite is about 97%.

Due to the impossibility to significantly reduce the phosphorus content in the concentrates using mechanical aloty for dissolution of phosphorus, contained in concentrates is 30 kg per 1 kg leachable phosphorus, i.e., significantly greater than the stoichiometry. Avoid re-precipitation of ferric sulfate, operated with pH values taken in the range of 1.6 to 1.4, depending on the content of solid particles in the pulp. The ratio of T:W was 1:2-1:3, and the total leaching time 50 min Obesfosforivanie was carried out in five cascading reactors located (10 minutes each).

Further processing of the concentrate was collected by means of work and firing the obtained pellets. When the sulfur content was reduced by 95% and phosphorus by about 80% (VIII international Congress on mineral processing, so 2, Leningrad, 1969, "Mekhanobr").

The disadvantage of this method is the complexity of the technological design of the leaching process, a high temperature process and a large iron loss solutions.

Known methods use as a mineral acid leaching of hydrochloric acid (patent PCT 93/10271, IMS 9-94). The essence of it is that before carry out leaching agglomeration of iron ore and leaching using hydrochloric sour the way, they use volatile hydrochloric acid, which is very harmful for staff and leads to corrosion of equipment due to the presence of hydrogen chloride.

Known methods of reducing the content of phosphorus in iron ore concentrates by the method of direct reduction of phosphorus by its translation in the slag (British mineral and petrographic group, Santa Barbara, February 2000). When the phosphorus content is reduced to 0.1%, and iron extraction is only 80,8%.

There is also known a method of direct reduction of phosphorus contained in iron ore concentrates by the injection of oxygen, air and lime dust in the Converter to demostratsii ore. This process was later improved by heating calcium oxide BOF gas. This allowed for the use of ore with a lower iron content and the phosphorus content of 3% or more, such as lepskii ore from 2.5-3.5% of phosphorus, and to obtain high-quality steel. ("Phosphorus in iron ore LIPI", Erzmetall, T. 50, 4 April 1997, S. 268-274).

The disadvantages of these methods must be attributed to economiccost, large iron loss (20%) and environmental issues.

The closest to offer those who slaskiego ridge", the authors are Tukino R. D., England C. M. (Australian Institute of mining and metallurgy /Avstral. IMM/, 5/97, S. 197-202).

They conducted experiments on obesfosforivanie iron ore concentrates acid leaching in the form of a thin pellets and particles.

It was found that chemical leaching is successful only if it is preceded by a heat treatment, which causes recrystallization of iron minerals in L - Fe2O3and concentrated phosphorus between grains of hematite. Heat treatment was roasting of the concentrate at a temperature of 500-600oC for 1-1 .5 hours, and leaching was used sulfuric acid in an amount of not less 110-150% of the stoichiometric with respect to phosphorus, at a temperature of 60-80oWith respect to T:W=1:3-1:5. The leaching time is 2-3 hours.

A disadvantage of the known technical solution is low phosphorus removal, as evidenced by the residual phosphorus content in the concentrate to about 40% of the original.

The technical task of the invention is the production of standard phosphorus iron ore concentrates. When you later use the CLASS="ptx2">

The technical result is achieved due to the optimum design parameters of the process of roasting and leaching that can extract iron about 95% and the phosphorus content in the concentrate is less than 0.25%.

To achieve a technical result in a well-known method of purification of iron ore concentrates, including preliminary roasting, acid leaching for the given parameters and the Department Vasilchenko residue (cake), changes, namely, the firing is carried out at a temperature of 800-1000oC for up to 1 hour. Leaching carry out mineral acid is sulfuric, nitric, and the specific choice of the acid is carried out depending on the mineralogical composition of the ore and the structure of matter, which is the carrier of phosphorus.

The temperature of the solution 20-50oS, and T:W =1:(1-2).

Differences between the proposed technical solutions from the prototype are the temperature and duration of calcination of iron ore concentrate, and the temperature of the leaching, the relations T:W and the control end of the process the residual acidity.

The choice of mineral acid to leach consider the example of iron ore one isye of them with different enrichment methods concentrates are characterized by high fotoritocco, as well as the presence of silica and alumina.

The content of phosphorus in different types of Lisakovsk ore according to many studies ranging from 0.6 to 0.8% and is explained by the presence of stilpnomelane (hydroxides of iron, enriched with phosphorus) and single grains of Apatite.

Found in the ore phosphate presents a white friable mass microspherocytosis patterns. Spherulites composing phosphate, and closely adjacent to each other. The size of the spherulites ranges from 0.004 to 0,018 mm calcium Phosphate is the main carrier of phosphorus in concentrates, because he is a minor part. Along with calcium phosphate in hydrogoethite first discovered the presence of alumophosphate, which by its lattice parameters meets the wavellite with iron ions.

Based on the characteristics of the mineralogical composition of raw materials and given the small proportion of compounds of calcium leaching was used sulphuric acid.

In the General case, sulfuric acid, it is advisable to apply at low concentrations of calcite (caso3in the concentrate, because in the process of leaching is not included sulfur in the formation of gypsum (CaS4), precipitated by f/L. It is known that the deposition of calcium in the form of sulphate takes place only after saturation of the solution.

When the content in the concentrate of calcite over 1% is advisable to use nitric acid, because in this case not paid sulfur because of the formation of soluble salts, which can be seen from reaction: caso3+ 2HN3= CA(NO3)2+ H2CO3.

The consumption of nitric acid is selected within 150-200% from stoichiometry in relation to phosphorus contained in the concentrate.

The parameters of the firing process were selected on the basis of the fact that in the given temperature range is the destruction of the structure of hydrohalite (FeOOH), recrystallization of iron and expulsion of phosphorus from grains on the phase boundary (crystals), forming a synthetic hematite 2FeOOH-->Fe2ABOUT3+H2Oh and phosphorus compounds.

As a result, access mineral acid to compounds of phosphorus and translating it into a solution.

At lower temperatures (less than 800o(C) the process proceeds with a lack of completeness. At higher temperatures (above 1000oC) is the sintering of the particles in the agglomerates and worsens the access of the acid to the particles of MINERGIE to 1 hour and provides high recovery of phosphorus in the solution during leaching. The increase in time of firing more than one hour, degrades techno-economic performance of the whole process dephosphorization.

The choice of the parameters of the leaching process was due mainly to the following two conditions: efficiency and completeness of its completion. The selected parameters are optimal, because with respect to T:W=1,2:1 decreases the consumption of acid, but the mixing of the pulp is very difficult and the pulp becomes non-uniform in composition and this may adversely affect the extraction of phosphorus. With respect to T: W more than 1:2 increasing the consumption of acid, i.e., reduced technical and economic indicators.

The temperature range within 20-50oWith selected based on the fact that depending on the firing temperature and the shutter speed for cooling the concentrate to a temperature of 20-50oWith no additional special equipment. When the temperature is less than 20oWith the pulp further cooling, at a temperature of more than 50oWith heat, i.e., the need for a refrigerator or heater. This complicates the instrumentation process and increases the cost of the process of dephosphorization.

Consider the implementation of the proposed method on the example of the purification of phosphorus is gravity-magnetic separation.

The result was obtained iron ore concentrate containing 48,73% iron, 0.6% phosphorus and 0.5% of calcium oxide.

Example 1: Taken linkage iron concentrate weighing 100 g and fired in a muffle furnace at a temperature of 900oC for one hour. The calcine is cooled to a temperature of 25oC, weighed and subjected to leaching with sulfuric acid having a concentration of 49% within one hour, with respect to T:W= 1: 1 and the consumption of acid, providing the residual contents in the solution after leaching within 6-10 g/l Suspension was stirred, and after the solution was filtered. The filter cake was washed with 50 ml of cold water.

Measured volume of the filtrate and wash water, and set them to a residual content of acid known methods, which amounted to 6 g/L.

The precipitate from the filter was dried at a temperature of 105oWith in an oven for 6 hours, weighed, ground, and it was determined the content of phosphorus and iron. The iron content was 56.4 per cent and phosphorus to 0.15%.

Iron loss amounted to 4.2%, and the extraction of phosphorus in solution is 79%. Other examples of implementation of the proposed method of dephosphorization source of iron ore concentrator is IU, below is the example of the method of dephosphorization in accordance with the parameters of the prototype and the example implementation using leaching of nitric acid for iron ore concentrate with a content of calcium oxide - 1,56% (example 20).

From the analysis results shown in the table, we can conclude.

The optimal mode is firing temperature of 900oTemperatures leaching 20-30oWhen the ratio of T:W=1:1-1:2.

In example 2, due to the low firing temperature of the iron and phosphorus does not meet the quality requirements of concentrate for further refining. Iron losses make up 9.2%, and the extraction of phosphorus less than 30%.

From example 6, we can conclude that the iron content and the extract obtained the best results, but the phosphorus content exceeds the permissible limits. This is because the firing temperature is higher than the optimal, and began the process of sintering, resulting in access of the acid to the particles is hindered in the leaching process, and hence removing phosphorus amounted to 29%. To obtain more satisfactory results requires significant uvelichilsa, the corresponding task. However, this is achieved due to the fact that the cooling of the roasted concentrate was increased from 1 hour to about 2 hours, which reduces the performance of the process obesfosforivanie. In the summer time to reach the temperature of the solution, so as not to degrade performance, you need a special additional cooling, i.e., the complexity of instrumentation.

From the analysis of example 11, it follows that increasing the solution temperature to 60oWith dramatically increases iron loss, which is about 8%.

Due to the rejection of the relations T:W (example 13), the content of phosphorus in iron ore concentrate exceeds the allowable value. This is because the pulp is very dense, hard and poorly mixed, the result of removing phosphorus is 55%.

The variance of the residual acidity of the solution (example 16), when it is equal to 3 g/l, indicates a lack of acid leaching, therefore, the degree of extraction of phosphorus is only 44%.

A large excess of acid allows you to achieve the task, as evidenced by the example 19, in which the residual acidity was 15 g/l, but is the defense and the prototype, selected by the authors, shows that almost all the examples (except 2 and 6) the results obtained are better than the prototype, despite a longer time of heat treatment of iron ore concentrate and temperature leaching. This is because the firing temperature is not sufficient for the recrystallization of iron, so removing phosphorus in solution is only 35%.

In example 20 as a mineral acid is used nitric acid under the same parameters of the leaching process, and sulfuric acid. Practically, despite the higher content of calcium oxide in the original concentrate, obtained a good result.

The choice of acid, in addition to the above considerations, is determined by specific local conditions, cost and availability in the region.

Based on the above we can conclude that the proposed solution has several advantages compared with the known technical solutions, namely:

1. The parameters of the firing process provide the recrystallization of iron and thus contributes to access mineral acid to the particles containing phosphorus.

2. Optimization of process parameters above is ursov and consumption of acid.

3. The resulting product, containing not less than 56% of iron and 0.15% phosphorus, which corresponds to the quality requirements applicable to iron ore concentrates for further use in the charge of metallurgical production.

Currently, the claimed technical solution passes pilot tested and will be used for the design of processing plants in several countries of the CIS and perhaps in foreign countries. In this regard, after analysis of industrial tests can be decided on foreign patenting.

1. The method of purification of iron ore concentrates from phosphorus, including roasting, cooling, leaching the concentrate with a mineral acid under given parameters of the leaching process, separating the liquid phase from the solid, characterized in that the iron ore concentrate is subjected to oxidizing roasting at a temperature of 800-1000oWith a shutter speed of no more than 1 h

2. The method according to p. 1, characterized in that depending on the mineralogical composition of iron ore concentrate as a mineral acid leaching using sulphuric or nitric acid.

3. The method according to any of paragraphs. 1 and 2, characterized in that the process you and a temperature of 20-50oC.

4. The method according to any of paragraphs. 1 and 2, characterized in that the process of leaching is performed with nitric acid, at a ratio of T: W= 1: (1-2) and a temperature of 20-50oC.

5. The method according to any of paragraphs. 1-4, characterized in that the leaching process is controlled by the final acidity of the solution and finish it at a value of pH 6-10 g/L.

 

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