Phosphorus is one of the steel smelting process, the major harmful elements. With the development of metallurgical industry, iron and steel enterprises demand for iron ore concentrate phosphorus content is higher and higher, so the development of iron ore Dephosphorizing efficient technology is imminent.
At present, the phosphorus reduction methods of high-phosphorus iron ore mainly include: 1 physical beneficiation method. The method is to finely grind the ore to the phosphorus mineral and the iron mineral to fully dissociate, and then reduce the phosphorus by magnetic separation, re-election or flotation, but the phosphorus-reducing effect is not ideal; 2 chemical beneficiation method. The method realizes phosphorus reduction by leaching iron ore with nitric acid, hydrochloric acid or sulfuric acid, and is a relatively effective method for reducing phosphorus, and the phosphorus mineral does not need to be completely dissociated, as long as it can be exposed to contact with the leachate. The purpose of reducing phosphorus can be achieved. However, this method consumes a large amount of acid and has a high cost. Moreover, it easily causes the dissolution of soluble iron minerals in the ore, resulting in the loss of iron. 3 microbial leaching method. The method mainly dissolves the phosphorus mineral by reducing the pH value of the system by microbial metabolic acid production, and the metabolized acid also chelate with the Ca 2+ , Mg 2+ , Al 3+ plasma to form a complex, thereby promoting the phosphate rock. Dissolution of matter. The problem is that it is still in the experimental stage, and there is still a big gap from the real industrialization. 4 smelting method. The method realizes dephosphorization by using phosphorus or alkali slag to form phosphorus slag in the molten iron before the molten iron is fed into the converter or the electric furnace. This method works very well, but it is costly and basically still in the basic research stage in China.
In this study, a new method, chlorination separation-weak magnetic separation process, was used to iron and phosphorus reduction of high-phosphorus iron ore.
First, test the ore sample
The test ore sample is a high-phosphorus iron ore sample in Yunnan, containing 41.56% iron and 1.13% phosphorus. Iron is mainly in the form of red limonite, siderite, iron silicate, magnetite. The weathering phenomenon of the sample is more serious. The original particle size composition is +5mm, which accounts for about 35%, -5+1mm, which accounts for about 45%, and -1mm, which accounts for about 20%. It is processed into less than 5mm before use.
The results of spectroscopic analysis, chemical analysis and iron phase analysis of the samples are shown in Tables 1 to 3. The results of particle size analysis after processing into -5 mm are shown in Table 4.
Table 1 Spectral analysis results of samples
Table 2 % of sample multi-element chemical analysis results
Table 3 Sample iron phase analysis results%
It can be seen from Tables 1 to 3 that the valuable elements recoverable in the sample are only iron, and other valuable elements such as copper , zinc , lead , molybdenum , nickel , cobalt , titanium , gold, silver, etc. are low; harmful elemental sulfur The arsenic content does not exceed the standard, but the phosphorus content is seriously exceeding the standard, which is 1.13%. The optional iron in the sample is iron in red limonite, siderite and magnetite, which account for 91.15% of the total iron.
Table 4 shows that iron and phosphorus are more evenly distributed at each particle size.
Table 4 - Particle size analysis results of -5mm sample
Second, the test process
The basic principle of chlorination is that the chlorinating agent is decomposed into highly active hydrogen chloride gas under high temperature; the hydrogen chloride gas reacts with the metal oxide in the ore to rapidly form volatile metal chloride; volatile metal chloride The compound is strongly adsorbed by the carbonaceous reducing agent, and the metal is isolated by the reducing atmosphere formed by the reducing agent and covers the surface of the reducing agent, and can be better recovered by beneficiation.
Chlorination segregation used to treat nickel, cobalt, and copper ore, and is a new method for treating iron ore. This experiment uses this method to carry out iron and phosphorus reduction research on a high-phosphorus iron ore in Yunnan. The test process is shown in Figure 1.
In the test, the type and amount of chlorinating agent, the type and amount of reducing agent, the temperature and time of carcination, the fineness of grinding product, and the influence of weak magnetic separation on the iron concentrate index were investigated. As used chlorinating agent, respectively L1, L2, L3, L4, respectively, reducing coke, lignite, anthracite, bituminous coal. The reducing agent is processed to -1mm for use.
Figure 1 Chlorination Segregation - Weak Magnetic Separation Test Procedure
It should be noted that the ore will have a certain loss on ignition after the isolation and roasting. Therefore, the iron concentrate recovery rate in the test is calculated for the isolated product.
Third, the test results and discussion
(1) Test of chlorinating agent type and dosage
The type and amount of chlorinating agent directly affect the formation of volatile metal chloride during chlorination and segregation, and thus affect the index of iron concentrate. In the case of reducing agent (coke) dosage of 10%, separation temperature of 1000 ° C, separation time of 60 min, weak magnetic selective magnetic induction strength of 0.12 T, and ball milling fineness of -0.074 mm accounting for 85.38%, respectively, different amounts are used. The four chlorinating agents were tested according to the flow of Figure 1, and the test results are shown in Figures 2 to 5.
Figure 2 Chloride agent L1 dosage test results
â– -Fe grade; â—†-P content; â–²-Fe recovery rate; â—-P recovery rate
Figure 3 Chloride agent L2 dosage test results
â– -Fe grade; â—†-P content; â–²-Fe recovery rate; â—-P recovery rate
Figure 4 chlorinating agent L3 dosage test results
â– -Fe grade; â—†-P content; â–²-Fe recovery rate; â—-P recovery rate
Figure 5 Chloride agent L4 dosage test results
â– -Fe grade; â—†-P content; â–²-Fe recovery rate; â—-P recovery rate
It can be seen from Fig. 2 to Fig. 5 that the effect of iron and phosphorus reduction by L1, L2, and 13 is not satisfactory, the iron grade of concentrate is low, and the phosphorus content is 0.30% or more. L4 has obvious effect of iron and phosphorus reduction. With the increase of its dosage, the iron grade and recovery rate of concentrates gradually increase, and the phosphorus content gradually decreases. When the dosage is 15%, the iron grade of concentrates reaches 75.25%. The phosphorus content decreased to 0.226% and the iron recovery rate was 82.32%. Thereafter, the concentrate index changed little. Therefore, L4 was selected as the chlorinating agent and the amount was determined to be 15%.
(2) Test of reducing agent type and dosage
The reducing agent plays a dual role of providing a reducing atmosphere and adsorbing volatile metal chloride as a carrier during the separation process. The solid reducing agents currently used are mainly coke, lignite, anthracite and bituminous coal, among which coke has the advantages of high strength, good reduction gas permeability and less impurities. The disadvantage is that the price is relatively expensive, and lignite, anthracite, bituminous coal Compared with coke, the price is low, but the ash is high, the impurities are many, and the ore is easily polluted. The four kinds of reductions were compared under the test conditions of 15% chlorinating agent L4, separation temperature 1000 ° C, separation time 60 min, weak magnetic selective magnetic induction strength 0.12 T, and ball milling fineness -0.074 mm accounting for 85.38%. The effect of the agent on the iron concentrate index, the test results are shown in Figures 6 to 9.
Figure 6 Lignite dosage test results
â– -Fe grade; â—†-P content; â–²-Fe recovery rate; â—-P recovery rate
Figure 7 results of bituminous coal test
â– -Fe grade; â—†-P content; â–²-Fe recovery rate; â—-recovery rate
Figure 8 Anthracite dosage test results
â– -Fe grade; â—†-P content; â–²-Fe recovery rate; â—-P recovery rate
Figure 9 Coke dosage test results
â– -Fe grade; â—†-P content; â–²-Fe recovery rate; â—-P recovery rate
It can be seen from Fig. 6 to Fig. 9 that when lignite, anthracite and bituminous coal are used as reducing agents, although the amount of reducing agent increases, the iron grade and iron recovery rate of concentrates gradually increase, and the phosphorus content gradually decreases, but the phosphorus content is always at 0.30. When coke is used as the reducing agent, the iron grade of the concentrate gradually increases with the increase of the amount of coke, and the iron recovery rate first increases and then decreases, and the phosphorus content does not exceed 0.30%, and it tends to decrease continuously. Therefore, coke was selected as the reducing agent, and the amount was determined to be 10%. At this time, the concentrate iron grade was 75.25%, the phosphorus content was 0.226%, and the iron recovery rate was 82.32%.
(III) Segregation temperature test
Since segregation is a chemical phase change process, temperature is one of the key factors. If the temperature is too low, it will not provide sufficient chemical reaction energy, which is not conducive to the reaction; on the contrary, if the temperature is too high, it will easily lead to softening and bonding of the ore, and the production cost is high in the future and the operation is difficult. In the case where the reducing agent coke amount is 10%, the chlorinating agent L4 dosage is 15%, the separation time is 60 min, the weak magnetic selective magnetic induction intensity is 0.12 T, and the ball milling fineness is -0.074 mm, accounting for 85.38%, according to the flow of Fig. 1 The isolation temperature test was carried out, and the test results are shown in Fig. 10.
Figure 10 Segregation temperature test results
â– -Fe grade; â—†-P content; â–²-Fe recovery rate; â—-P recovery rate
Figure 10 shows that with the increase of temperature, the concentrate iron grade and iron recovery rate first increase and then decrease, the phosphorus content decreases first and then increases; in addition, during the roasting process, the temperature is 1050. At °C, the ore has a softening and bonding phenomenon. When the temperature continues to rise to 1100 °C, more than 80% of the ore is bonded together, affecting the selection index. Considering that the calcination temperature is 1000 °C, it is suitable to obtain iron concentrate with iron grade of 75.27%, phosphorus content of 0.227% and iron recovery of 82.62%.
(4) Segregation time test
Under certain other conditions, the longer the segregation time, the more thorough the segregation reaction, but at the same time, the other elements have more opportunities to participate in the reaction and affect the iron concentrate index; otherwise, the segregation time is too short, effective The positive reaction cannot be completely completed and will also affect the iron concentrate index. In the reducing agent coke dosage is 10%, the chlorinating agent L4 dosage is 15%, the isolation temperature is 1000 ° C, the weak magnetic selective magnetic induction strength is 0.12T, and the ball milling fineness is -0.074mm accounting for 85.38%, according to Figure 1 The process is subjected to an isolation time test, and the test results are shown in Fig. 11.
Figure 11 Segregation time test results
â– -Fe grade; â—†-P content; â–²-Fe recovery rate; â—-P recovery rate
Figure 11 shows that with the extension of the separation time, the iron grade and iron recovery rate of concentrates increased first and then decreased, and the phosphorus content decreased first and then increased, but the degree of change of these indicators was relatively small. Considering comprehensively, the separation time was determined to be 45 min. At this time, the concentrate iron grade was 76.06%, the phosphorus content was 0.217%, and the iron recovery rate was 83.11%.
(5) Weak magnetic selective magnetic induction strength test
In the case where the reducing agent coke amount is 10%, the chlorinating agent L4 dosage is 15%, the separation temperature is 1000 ° C, the separation time is 45 min, and the ball milling fineness is -0.074 mm, accounting for 85.38%, the weak magnetic field is performed according to the flow of FIG. The magnetic induction strength test is selected, and the test results are shown in Table 5.
It can be seen from Table 5 that as the magnetic induction strength of weak magnetic separation increases, the grade of concentrate iron gradually decreases, and the iron recovery rate and phosphorus content gradually increase. Taking into account various indicators, the magnetic induction strength of the weak magnetic selection is selected to be 0.16T.
(6) Ball Mill fineness test
In the case of reducing agent coke dosage of 10%, chlorinating agent L4 dosage of 15%, separation temperature of 1000 ° C, separation time of 45 min, weak magnetic separation magnetic induction intensity of 0.16 T, ball milling fineness test according to the flow of Figure 1 The test results are shown in Table 6.
Table 5 Weak magnetic selective magnetic induction test results
Note: The ore burnout rate = 9.68%, the isolated product Fe grade is 46.05, and the P content is 1.26%. The same below.
Table 6 Ball Milling Fineness Test Results%
Table 6 shows that as the fineness of the ball mill increases, the grade of concentrate iron gradually increases, the phosphorus content gradually decreases, and the iron recovery rate first rises and then decreases. Taking into account the concentrate index and grinding cost, the ball mill fineness is selected to be -0.074mm, accounting for 85.38%.
(7) Repeated test of comprehensive process conditions
Through the above tests, the comprehensive conditions of the whole process were determined to be 10% coke dosage, 15% chlorinating agent L4, 1000°C separation temperature, 45 min separation time, 85.38% ball milling fineness-0.074 mm, and weak magnetic selective magnetic induction strength 0.16T. . Repeat the test in the whole process according to the comprehensive conditions. The test results are shown in Table 7.
Table 7 full process comprehensive conditions repeated test results%
It can be seen from Table 7 that the chlorination separation-weak magnetic separation treatment of the test ore sample can achieve good iron and phosphorus reduction effect, and the iron concentrate yield (for the isolated product) is 50.88%~ 52.00%, iron grade is 75.33% ~ 76.44%, phosphorus content is 0.215% ~ 0.218%, SiO 2 content is 5.44% ~ 6.01%, iron recovery (on the isolated product) is 83.63% ~ 85.66%.
Fourth, the conclusion
(1) The iron ore of an iron ore in Yunnan is mainly red limonite and siderite, and the phosphorus content is high. It is difficult to obtain the ideal selection index by conventional mineral processing.
(2) The amount of coke in the reducing agent is 10%, the amount of chlorinating agent L4 is 15%, the separation temperature is 1000 °C, the separation time is 45 min, the grinding fineness is -0.074 mm, accounting for 85.38%, and the weak magnetic selective magnetic induction intensity is Under the condition of 0.16T, the ore is treated by chlorination-separation-weak magnetic separation process, and the iron concentrate grade is above 75.33%, the phosphorus content is below 0.218%, and the iron recovery rate is above 83.63%.
(3) The use of chlorination-separation-weak magnetic separation process for high-phosphorus iron ore is a new method for iron and phosphorus reduction. A large number of experimental studies have shown that the process can achieve better beneficiation index for high-phosphorus-like hematite ore, high-phosphorus iron ore, high-phosphorus-sulfur-arsenic refractory iron ore.
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