Hebei Steel Group iron ore mining company located in Sijiaying Luan County in Hebei Province, TFe ore grade of 29.38%. The Sijiaying Iron Mine North District began preparations as early as 1958, and it has lasted for half a century. During this period, geological resources exploration, water source exploration, engineering geological exploration, topographic survey, ore dressing test, tailings high concentration transport test, sewage A lot of work, such as handling experiments, environmental assessment, feasibility studies, and preliminary design. However, technical and economic problems such as red mine sorting, mining area water, stripping ratio, tailings and waste rock stacking have been plagued by the development of Sijiaying Iron Mine. After years of unremitting efforts by relevant domestic research institutes, it has successfully solved various problems affecting mine development. Especially in the 1990s, the ore dressing in Anshan District has made major breakthroughs, which promoted the development of Sijiaying Iron Mine. Construction.

On this basis, in May 2003, the first phase of the Sijiaying project was started. The scale of the oxidized ore was 6 million t/a, and the scale of the primary mine was 1 million t/a. It was completed and put into operation in September 2007. The concentrate is 2.54 million tons and the iron concentrate grade is 66%. The first phase of the Sijiaying Iron Mine uses a stage grinding process, a coarse subdivision, a re-election-high gradient strong magnetic separation-anion reverse flotation process, although many studies have shown that this process is basically well adapted to the Sijiaying The selection of ore, but since the production, there is a big gap between actual production and design. The concentrate grade is always around 63%, and the recovery rate can only reach 45%. At the same time, some design problems are gradually exposed. It restricts the production and economic benefits of the mine. To this end, the mining company organized relevant personnel to tackle the specific problems existing in the mineral processing, and proposed reasonable process parameters and pharmaceutical systems suitable for mineral processing, so that the iron concentrate grade and recovery rate were increased to 65.50% and 70.00%, respectively. Significant economic and social benefits have been achieved.

First, the nature of the ore

(1) Multi-element analysis of ore and analysis of iron phase. The results of multi-element chemical analysis and iron phase analysis of raw ore are shown in Tables 1 and 2, respectively.

Table 1 Multi-element chemical analysis results of ore

Table 2 Iron phase analysis results of ore

(2) Mineral composition and embedding characteristics of ore. Sijiaying Anshan Iron ore belongs to, sedimentary rocks, shallow to hematite quartzite, quartz rock deep transition to a magnet. Simple ore mineral composition, mainly magnetite, hematite illusion, secondary hematite; gangue minerals quartz, followed by the actinolite, amphibole mineral, apatite inclusions angle and a small amount of ordinary amphibole and pyroxene; trace mineral apatite, pyrite, copper ore, in addition to the post-alteration chlorite, biotite and carbonate minerals. The ore sample taken in this test is a shallow lean hematite.

The ore structure is dominated by strips with a wrinkled structure. The structure of the ore is mainly composed of granular crystal structure and metasomatic structure. In the iron mineral band, the magnetite is semi-self-shaped and self-morphing, and the particle size is not uniform, while the magnetite inclusions in quartz are It has a small self-crystal structure. Oxidative metasomatism occurs in the periphery of magnetite and in cleavage cracks, forming edge metasomatism, network and residual structure.

The average embedding particle size of the iron mineral was measured to be 62.79 μm, and the average embedding particle size of the gangue mineral was 80.25 μm.

Second, the original process flow problems

(1) Original process

After the ore is crushed, it enters the grinding and selection system. The grinding, re-election, concentration, and magnetic separation systems are four series, and the concentrated flotation system is two series. The ore stored in the grinding bin is given to the first φ3.6m×5.0m lattice ball mill by the belt conveyor, the classifier is φ3m double spiral classifier; the second section mill is φ3.6m×5.0m overflow ball mill The classifier is a φ500mm hydrocyclone group. After two stages of continuous grinding, the φ500mm hydrocyclone component grade is used, and the coarse fraction is coarsely selected and selected by φ1.5m spiral chute to produce re-elected concentrate. The spiral tailing coarsely selected tailings enters SLon-1750 type. In the magnetic selection of medium magnetic machine, the tailings of the medium magnetic machine is the final tailings, the selected medium mine of the spiral chute is directly returned to the spiral chute selection, the selected tailings of the spiral chute and the magnetic separation concentrate of the medium magnetic machine are merged into the third stage grinding. Mine classification circuit. The third-stage mill is a φ3.6m×6.0m overflow ball mill, the closed-circuit grading equipment is a φ500mm hydrocyclone group, and the third-stage classifier overflows to the grading before re-election. Before the re-election, the overflow size of the classifier is -200 mesh, accounting for 95%. It enters the magnetic separation of the CTB-1230 weak magnetic field separator. The weak magnetic field magnetic separator tailings enters the φ50m thickener before the strong magnetic separation, and then passes through the circle after concentration. The slag is removed from the cylinder and enters the magnetic separation of the SLon-1750 high-gradient magnetic separator. The tailings of the high-gradient magnetic separator are the final tailings. The weak magnetic field magnetic separator and the high gradient strong magnetic separator concentrate enter the φ50m thickener before reverse flotation, and then enter the reverse flotation operation after concentration. After 1 rough selection and 1 selection, the final flotation concentrate is produced. The flotation selected tailings are returned to the reverse flotation rough selection operation, and the reverse flotation coarse selection tailings is subjected to 2 reverse flotation sweeps to produce the final tailings.

(2) Problems in the original production process

At the initial stage of production, affected by factors such as ore properties, production process factors and actual production processes, the original production process has the following problems in the actual production process:

1. Due to the high degree of weathering of the ore surface, serious muddying and insufficient improvement of the circulating water purification system in the production process, a large amount of slime is accumulated in the process, resulting in a maximum concentration of overflow water of φ30m clarifier. , resulting in high grade tailings beneficiation, metal recovery rate is low, circulating pump wear too fast.

2. The three-stage grinding causes the content of -10μm to increase the content of the grain. The high mud content seriously affects the selectivity of the anti-flotation agent, which is not conducive to the normal sorting of the reverse flotation operation, and also causes the sweeping magnetic tailings and high gradient magnetic field. The tailings grade is high.

3. The proportion of the hydrocyclone is unreasonable. The ratio of the amount of re-elected ore entering the re-floating ore is only 2:1 (design index is 4:1), resulting in a large amount of rough-sorting tail chute tailings. The high grade makes the medium magnetic tailings too high, and the metal loss is serious; the low-cost re-election concentrate production is low, and the high-cost flotation concentrate production is high, resulting in higher comprehensive ore beneficiation cost.

4. The high gradient magnetic separator has insufficient capacity. Before the strong magnetic field, the concentrated overflow flow is large, the concentration is high (generally greater than 4.5%), and the overflow grade exceeds 24%, resulting in a high grade of integrated tailings.

5, the filtration workshop often occurs mining accidents, the filtration capacity is seriously insufficient, resulting in a silt in the filtration workshop, many motors are submerged, and two ore-concentrating machines before filtration also have multiple crushing accidents. After many investigations, it was found that the reverse flotation concentrate contained starch, and its viscosity caused the micropores of the ceramic filter plate to be clogged, resulting in extremely poor filtration effect. It was necessary to add concentrated sulfuric acid to remove the starch. After using concentrated sulfuric acid, the utilization coefficient of the ceramic filter is basically about 0.5t/(m ² ·h). Due to the number of spare units, only 10 units can be operated. The daily capacity of the filtration workshop is about 3000t, which can only meet the previous two red mines. Series and 1 magnetic mine series production.

Third, the process improvement and production practice of the concentrator

(1) Transformation of production circulating water purification system

In view of the problem that the production circulating water concentration is too high and the ore dressing production is seriously constrained, the plant first carried out the on-site dynamic simulation test. Based on the actual situation of the existing purification system, the center tube and overflow weir of the φ30m clarifier were determined. At the same time, based on the conditions of flocculant type and dosage, the A ^# anionic polymer polyacrylamide was screened for semi-industrial test, and the dosing system was proposed and implemented. After on-site inspection, the production cycle water was basically stable after 3 days of circulation, and the feed water concentration of φ30m clarifier decreased from 9.31% to 3.50%, and the concentration of purified water suspension was below 0.10%. The amount is basically stable at about 0.7 g/m ³ .

After the transformation of the production circulating water purification system, the comprehensive concentrate grade increased by 0.50%, the integrated tailings grade decreased by 5.00%, the metal recovery rate increased by 15.20%, and the beneficiation ratio decreased by 0.84. At the same time, due to the substantial reduction of the mud content of the slurry in the process of production circulating water purification, the technical parameters of the reverse flotation operation were optimized, the grade of the reverse flotation concentrate was increased by 1.45 percentage points, and the grade of the reverse flotation tailings decreased by 1.73 percentage points. , laid the foundation for future process optimization, quality improvement and tailing.

(II) Three-to-one transformation of the three-stage grinding machine

In the original process design, the effective utilization coefficient of the three-stage mill is 0.95t/(h·m ³ ). In the whole process of the second oxidation ore in 2008, the effective utilization coefficient of the three-stage mill was only 0.395t/(h· m ³ ), compared with the design, the gap is large, indicating that the three sections have a lot of grinding capacity. In response to the problem of over-grinding and over-capacity of the three-stage mill, the company has developed a two-stage three-stage grinding machine with a series of three-stage grinders, which means that only one series of three-stage hydrocyclone units will be demolished. In another series, the three-stage mill discharges the ore back to the series of two-stage hydrocyclone to the mine pump pool without adding power equipment. After implementing the “two-to-one” transformation of the three-stage mill, the utilization coefficient of the three-stage mill was increased from 0.39t/(h·m ³ ) to 0.91t/(h·m ³ ), which is close to the design level; The throughput of machine ore is increased to 192.07t/h, which is equivalent to the design of 190.91t/h; the throughput per unit volume reaches 7.11t/h. In addition, the process test report shows that, in the case that the grinding treatment volume is not reduced, the refined ore grade and the reverse flotation concentrate grade before and after the reform are equivalent, but the medium magnetic field magnetic separator tailing grade and the high gradient strong magnetic separator The tailings grade and the reverse flotation tailings grade have different degrees of reduction, indicating that with the increase of the three-stage mill processing capacity, the over-grinding phenomenon is significantly reduced, the mineral processing technical indicators have been further optimized, and the transformation has been successful. At the same time, after stopping two φ3.6m×6m overflow ball mills, it can save 2400t of steel balls and save 1.8 million kW·h every year, with remarkable economic benefits.

(III) Test and adjustment of process parameters of hydrocyclone

The discharge size of the hydrocyclone can not meet the actual production, and the proportion of the coarse subdivision grade is seriously out of balance. Through a large amount of data analysis and comparison, the hydrostatic cyclone overflow pipe is adjusted from 160mm to 120mm, and the grit nozzle is adjusted from 80mm to 90mm. The three-stage hydrocyclone sinking nozzle is adjusted from 90mm to 75mm. At the same time, the hydrocyclone feeding mine automation operating system is improved, and the diameter of the water supply pipe to the mine pump pool is adjusted from φ50mm to φ159mm, and the motor frequency is adjusted according to the pump pool liquid level, according to the pump pool liquid level and hydrocyclone. The working pressure is supplemented by water. After the above transformation, the re-election concentrate grade can be basically stabilized at 65.50%, and the grade of medium and strong magnetic separator tailings is reduced from the original 17% to about 12%; especially the adjustment of the sinking nozzle of the second-stage hydrocyclone After that, the proportion of its coarse subdivision is greatly improved, and the basic capacity can reach 7:3. The number of single-series re-selected spiral chutes is more than 18, which increases the output of re-election concentrate and effectively reduces the circulation of the mine. It also plays an important role in reducing over-grinding and reducing tailings grade; it also creates better conditions for the operation of the reverse flotation system and enhances the controllability of anti-flotation indicators. At present, the grade of reverse flotation concentrate can reach more than 66%, and the grade of reverse flotation tailings is reduced from 25% to 22%.

The improvement of the hydrocyclone feeding automation operating system has been adjusted from the hydrocyclone to the mine pump pool, the automatic operation ideas and the automatic operation mode. After the transformation, the diameter of the water pipe supplied by the hydrocyclone to the mine pump pool is φ159mm, and the water is automatically added according to the pump tank liquid level and the hydraulic cyclone working pressure. Due to the stable working pressure of the hydrocyclone, the working state of the hydrocyclone has been improved. At present, the automatic operation level of the hydrocyclone is relatively mature, so the working state and classification efficiency of the hydrocyclone are improved.

(4) High-gradient strong magnetic separator expansion

In the first phase design, the high-gradient strong magnetic separator before the slag screening machine is a cylindrical sieve, which is easy to block, the slag removal effect is not good, the sieve top material enters the tailings or the return process, and the single series tailings grade is above 17%. Due to the insufficient capacity of the high-gradient magnetic separator, the overflow of the thickener before the high-gradient magnetic separation is too large, and the concentration is high (generally greater than 4.5%), and the overflow grade is above 24%, resulting in a high grade of integrated tailings. Metal loss is serious. After many process investigations and analysis and argumentation, the proportion of the second-stage hydrocyclone is adjusted first, followed by the re-election to increase the sweeping and re-engineering. Under the premise of re-electing more qualified concentrates, try to reduce the high gradient. The magnetic content of the magnetic separation, but the ability of the high gradient strong magnetic separator is still insufficient, and the tailings grade remains high. During the period from April to August 2008, another φ2000 mm high-gradient magnetic separator was installed in the 3 series. The results showed that the grades of the three high-gradient magnetic separation tailings were significantly lower than the two high gradients. Strong magnetic separation of tailings grade.

In order to reduce the grade of tailings and improve the processing capacity of high-gradient magnetic separators, in September 2008, one SLon-2000 high-gradient magnetic separator was added to each series, and the single-series high-gradient magnetic separation processing capacity was increased to 110～180t/h, at the same time, the original medium-magnetic front cylinder screen was changed to a flat screen, which optimized the working conditions of the medium magnetic machine and played a positive role in the purification process. After the completion of the transformation, the grade of medium and strong magnetic separation tailings decreased from 17% to about 12%. The overflow concentration of the thickener before the strong magnetic separation also fell below 3.0%, and the overflow grade was lower than 23%. The effect was very obvious, so the effect was very obvious. The high-gradient magnetic separator expansion project has played a positive role in improving concentrate production.

(V) Filtration workshop capacity expansion

The original design equipment of the filtration workshop was selected as 12 P30/10-C-1 ceramic filters, and the filter utilization factor was 1.0t/(m ² ·h). After the flotation plant started running, the filter utilization factor was very low. In June 2008, four new TT-60 ceramic filters and two PZG-96 disc filters were added. The production capacity of PZG-96 disc filter is 60-120t/h. After the expansion of the filtration workshop, the total filtration area will increase from 360m ² to 792m ² , and the iron concentrate powder will be processed above 6500 t/d. The five series of the beneficiation plant can operate normally.

Fourth, the conclusion

(1) Since the first phase of the Sijiaying Iron Ore Dressing Plant was officially put into operation in 2007, after many technical improvements, the oxidizing ore process has made great technological progress, and various economic and technical indicators have been continuously improved. The grade of concentrate was increased from 63.00% before the transformation to 65.50%, and the metal recovery rate was increased from 45.00% before transformation to 70.00%. The economic and social benefits are very significant. However, at the same time, as the mining conditions deepen and the local quality conditions change greatly, how to maintain and improve the existing production indicators and reach the advanced production level is the main work and research direction to be carried out in the next step.

(2) At present, oxidized ore beneficiation technology has been successfully applied in some iron ore dressing plants in China. However, due to different mine geology and different ore dressing conditions, oxidized ore beneficiation technology is also different, and a beneficiation method suitable for the ore properties of Sijiaying iron ore is established. It has important practical application and popularization value for enriching and perfecting China's oxidized ore beneficiation technology and theory, and promoting the sustainable development of mine oxidized ore beneficiation technology in China.

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